diff --git a/app/app/api/cards/[cardId]/route.ts b/app/app/api/cards/[cardId]/route.ts
new file mode 100644
index 0000000..09315f9
--- /dev/null
+++ b/app/app/api/cards/[cardId]/route.ts
@@ -0,0 +1,162 @@
+import { NextRequest, NextResponse } from "next/server";
+import { getCardStorage } from "@/lib/services/cardStorage";
+import { createBaseCard, validateCardInput } from "@/lib/services/cardTemplating";
+
+/**
+ * GET /api/cards/[cardId]
+ * Retrieves a specific card by ID.
+ */
+export async function GET(
+  request: NextRequest,
+  { params }: { params: { cardId: string } }
+) {
+  try {
+    const userId = request.headers.get("x-user-id") ?? "demo-user";
+    
+    if (!userId) {
+      return NextResponse.json(
+        { error: "Unauthorized" },
+        { status: 401 }
+      );
+    }
+
+    const storage = getCardStorage();
+    const card = await storage.getCard(userId, params.cardId);
+
+    if (!card) {
+      return NextResponse.json(
+        { error: "Card not found" },
+        { status: 404 }
+      );
+    }
+
+    return NextResponse.json(
+      { 
+        success: true, 
+        card 
+      },
+      { status: 200 }
+    );
+
+  } catch (error) {
+    console.error("Error fetching card:", error);
+    return NextResponse.json(
+      { 
+        error: "Failed to fetch card",
+        details: error instanceof Error ? error.message : "Unknown error"
+      },
+      { status: 500 }
+    );
+  }
+}
+
+/**
+ * PUT /api/cards/[cardId]
+ * Updates an existing card (creates a new version).
+ */
+export async function PUT(
+  request: NextRequest,
+  { params }: { params: { cardId: string } }
+) {
+  try {
+    const userId = request.headers.get("x-user-id") ?? "demo-user";
+    
+    if (!userId) {
+      return NextResponse.json(
+        { error: "Unauthorized" },
+        { status: 401 }
+      );
+    }
+
+    const storage = getCardStorage();
+    const existingCard = await storage.getCard(userId, params.cardId);
+
+    if (!existingCard) {
+      return NextResponse.json(
+        { error: "Card not found" },
+        { status: 404 }
+      );
+    }
+
+    const body = await request.json();
+
+    // Validate input
+    try {
+      validateCardInput(body);
+    } catch (validationError) {
+      return NextResponse.json(
+        { 
+          error: "Invalid input", 
+          details: validationError instanceof Error ? validationError.message : "Unknown error"
+        },
+        { status: 400 }
+      );
+    }
+
+    // Create new version of the card with the same ID
+    const updatedCard = createBaseCard(body);
+    updatedCard.cardId = params.cardId; // Preserve the original card ID
+
+    await storage.updateCard(userId, updatedCard);
+
+    return NextResponse.json(
+      { 
+        success: true, 
+        card: updatedCard,
+        message: "Card updated successfully" 
+      },
+      { status: 200 }
+    );
+
+  } catch (error) {
+    console.error("Error updating card:", error);
+    return NextResponse.json(
+      { 
+        error: "Failed to update card",
+        details: error instanceof Error ? error.message : "Unknown error"
+      },
+      { status: 500 }
+    );
+  }
+}
+
+/**
+ * DELETE /api/cards/[cardId]
+ * Deletes a card from the user's profile.
+ */
+export async function DELETE(
+  request: NextRequest,
+  { params }: { params: { cardId: string } }
+) {
+  try {
+    const userId = request.headers.get("x-user-id") ?? "demo-user";
+    
+    if (!userId) {
+      return NextResponse.json(
+        { error: "Unauthorized" },
+        { status: 401 }
+      );
+    }
+
+    const storage = getCardStorage();
+    await storage.deleteCard(userId, params.cardId);
+
+    return NextResponse.json(
+      { 
+        success: true,
+        message: "Card deleted successfully" 
+      },
+      { status: 200 }
+    );
+
+  } catch (error) {
+    console.error("Error deleting card:", error);
+    return NextResponse.json(
+      { 
+        error: "Failed to delete card",
+        details: error instanceof Error ? error.message : "Unknown error"
+      },
+      { status: 500 }
+    );
+  }
+}
diff --git a/app/app/api/cards/route.ts b/app/app/api/cards/route.ts
new file mode 100644
index 0000000..642ca17
--- /dev/null
+++ b/app/app/api/cards/route.ts
@@ -0,0 +1,105 @@
+import { NextRequest, NextResponse } from "next/server";
+import { createBaseCard, validateCardInput } from "@/lib/services/cardTemplating";
+import { getCardStorage } from "@/lib/services/cardStorage";
+
+/**
+ * POST /api/cards
+ * Creates a new card and saves it to the user's profile.
+ * 
+ * Request body should match BaseCardInput interface.
+ * Returns the created card with its generated ID.
+ */
+export async function POST(request: NextRequest) {
+  try {
+    // TODO: Replace with actual auth - get userId from session
+    const userId = request.headers.get("x-user-id") ?? "demo-user";
+    
+    if (!userId) {
+      return NextResponse.json(
+        { error: "Unauthorized" },
+        { status: 401 }
+      );
+    }
+
+    const body = await request.json();
+
+    // Validate input
+    try {
+      validateCardInput(body);
+    } catch (validationError) {
+      return NextResponse.json(
+        { 
+          error: "Invalid input", 
+          details: validationError instanceof Error ? validationError.message : "Unknown error"
+        },
+        { status: 400 }
+      );
+    }
+
+    // Create the card
+    const card = createBaseCard(body);
+
+    // Save to storage
+    const storage = getCardStorage();
+    await storage.saveCard(userId, card);
+
+    return NextResponse.json(
+      { 
+        success: true, 
+        card,
+        message: "Card created successfully" 
+      },
+      { status: 201 }
+    );
+
+  } catch (error) {
+    console.error("Error creating card:", error);
+    return NextResponse.json(
+      { 
+        error: "Failed to create card",
+        details: error instanceof Error ? error.message : "Unknown error"
+      },
+      { status: 500 }
+    );
+  }
+}
+
+/**
+ * GET /api/cards
+ * Retrieves all cards for the authenticated user.
+ */
+export async function GET(request: NextRequest) {
+  try {
+    // TODO: Replace with actual auth
+    const userId = request.headers.get("x-user-id") ?? "demo-user";
+    
+    if (!userId) {
+      return NextResponse.json(
+        { error: "Unauthorized" },
+        { status: 401 }
+      );
+    }
+
+    const storage = getCardStorage();
+    const cards = await storage.getUserCards(userId);
+
+    return NextResponse.json(
+      { 
+        success: true, 
+        cards,
+        count: cards.length 
+      },
+      { status: 200 }
+    );
+
+  } catch (error) {
+    console.error("Error fetching cards:", error);
+    return NextResponse.json(
+      { 
+        error: "Failed to fetch cards",
+        details: error instanceof Error ? error.message : "Unknown error"
+      },
+      { status: 500 }
+    );
+  }
+}
diff --git a/app/lib/services/README.md b/app/lib/services/README.md
new file mode 100644
index 0000000..44ab1e1
--- /dev/null
+++ b/app/lib/services/README.md
@@ -0,0 +1,76 @@
+# Card Templating & Storage Services
+
+This directory contains the core services for creating and persisting language learning cards.
+
+## Quick Start
+
+```typescript
+import { createBaseCard } from "./cardTemplating";
+import { getCardStorage } from "./cardStorage";
+
+// 1. Create a card from AI-generated data
+const card = createBaseCard({
+  language: "Spanish",
+  lemma: "hablar",
+  partOfSpeech: "verb",
+  definitions: [
+    { definition: "to speak, to talk" }
+  ],
+  examples: [
+    { sentence: "Ella habla tres idiomas." }
+  ],
+  ipa: "aˈβlaɾ"
+});
+
+// 2. Save to user profile
+const storage = getCardStorage();
+await storage.saveCard("user-123", card);
+```
+
+## Architecture
+
+### cardTemplating.ts
+- **`createBaseCard(input)`** - Templates linguistic data into standardized JSON
+- **`validateCardInput(input)`** - Validates input before card creation
+- **`createBaseCardBatch(inputs)`** - Bulk card creation
+
+### cardStorage.ts
+- **Abstract interface** - `CardStorageProvider` for database-agnostic persistence
+- **In-memory implementation** - For testing and development
+- **Factory function** - `getCardStorage()` returns configured provider
+
+## API Routes
+
+- `POST /api/cards` - Create new card
+- `GET /api/cards` - Get all user's cards
+- `GET /api/cards/[cardId]` - Get specific card
+- `PUT /api/cards/[cardId]` - Update card (versioned)
+- `DELETE /api/cards/[cardId]` - Delete card
+
+## Best Practices
+
+✅ **DO:**
+- Keep cards immutable once learned
+- Version cards instead of regenerating IDs
+- Validate input before card creation
+- Use the abstract storage interface for flexibility
+- Attach learning progress separately from cards
+
+❌ **DON'T:**
+- Let LLMs write directly to database
+- Regenerate card IDs on edits
+- Store progress data inside cards
+- Skip input validation
+
+## Testing
+
+```typescript
+import { InMemoryCardStorage } from "./cardStorage";
+
+const storage = new InMemoryCardStorage();
+const card = createBaseCard(testInput);
+await storage.saveCard("test-user", card);
+
+const retrieved = await storage.getCard("test-user", card.cardId);
+expect(retrieved).toEqual(card);
+```
diff --git a/app/lib/services/cardStorage.ts b/app/lib/services/cardStorage.ts
new file mode 100644
index 0000000..a5f0a5b
--- /dev/null
+++ b/app/lib/services/cardStorage.ts
@@ -0,0 +1,92 @@
+import type { BaseCard } from "../types/card.types";
+
+/**
+ * Abstract storage interface for card persistence.
+ * Implement this interface with your actual database (DynamoDB, PostgreSQL, etc.)
+ */
+export interface CardStorageProvider {
+  /**
+   * Save a card to a user's profile
+   */
+  saveCard(userId: string, card: BaseCard): Promise<void>;
+
+  /**
+   * Get all cards for a user
+   */
+  getUserCards(userId: string): Promise<BaseCard[]>;
+
+  /**
+   * Get a specific card by ID
+   */
+  getCard(userId: string, cardId: string): Promise<BaseCard | null>;
+
+  /**
+   * Delete a card from a user's profile
+   */
+  deleteCard(userId: string, cardId: string): Promise<void>;
+
+  /**
+   * Update an existing card (versioning)
+   */
+  updateCard(userId: string, card: BaseCard): Promise<void>;
+}
+
+/**
+ * In-memory storage implementation for testing and development.
+ * DO NOT use in production.
+ */
+export class InMemoryCardStorage implements CardStorageProvider {
+  private storage: Map<string, Map<string, BaseCard>> = new Map();
+
+  async saveCard(userId: string, card: BaseCard): Promise<void> {
+    if (!this.storage.has(userId)) {
+      this.storage.set(userId, new Map());
+    }
+    
+    this.storage.get(userId)!.set(card.cardId, card);
+  }
+
+  async getUserCards(userId: string): Promise<BaseCard[]> {
+    const userCards = this.storage.get(userId);
+    if (!userCards) return [];
+    
+    return Array.from(userCards.values());
+  }
+
+  async getCard(userId: string, cardId: string): Promise<BaseCard | null> {
+    return this.storage.get(userId)?.get(cardId) ?? null;
+  }
+
+  async deleteCard(userId: string, cardId: string): Promise<void> {
+    this.storage.get(userId)?.delete(cardId);
+  }
+
+  async updateCard(userId: string, card: BaseCard): Promise<void> {
+    const updatedCard = {
+      ...card,
+      version: incrementVersion(card.version)
+    };
+    
+    await this.saveCard(userId, updatedCard);
+  }
+}
+
+/**
+ * Increments a semantic version string (e.g., "1.0" -> "1.1")
+ */
+function incrementVersion(version: string): string {
+  const parts = version.split(".");
+  const minor = parseInt(parts[1] ?? "0", 10) + 1;
+  return `${parts[0]}.${minor}`;
+}
+
+/**
+ * Factory function to get the appropriate storage provider.
+ * Currently returns in-memory storage for development.
+ * Can be extended to support DynamoDB or other backends.
+ */
+export function getCardStorage(): CardStorageProvider {
+  // For now, always use in-memory storage
+  // To add DynamoDB support, install @aws-sdk packages and configure via env vars
+  return new InMemoryCardStorage();
+}
diff --git a/app/lib/services/cardTemplating.ts b/app/lib/services/cardTemplating.ts
new file mode 100644
index 0000000..d74dcdc
--- /dev/null
+++ b/app/lib/services/cardTemplating.ts
@@ -0,0 +1,130 @@
+import { randomUUID } from "crypto";
+import type { BaseCardInput, BaseCard } from "../types/card.types";
+
+/**
+ * Creates a fully-formed baseCard from validated input data.
+ * This function templates linguistic data into a standardized JSON structure.
+ * 
+ * @param input - Validated linguistic data from AI pipeline or upstream service
+ * @returns A complete BaseCard object ready for persistence
+ */
+export function createBaseCard(input: BaseCardInput): BaseCard {
+  const now = new Date().toISOString();
+
+  return {
+    cardId: randomUUID(),
+    language: input.language,
+    lemma: input.lemma,
+    normalizedLemma: input.lemma.toLowerCase().trim(),
+
+    partOfSpeech: input.partOfSpeech,
+    otherForms: [],
+
+    phonetics: {
+      ipa: input.ipa ?? "",
+      respelling: ""
+    },
+
+    definitions: input.definitions.map(d => ({
+      definition: d.definition,
+      register: d.register ?? "neutral",
+      domain: d.domain ?? "general",
+      confidence: 0.9
+    })),
+
+    coreMeaning: input.definitions[0]?.definition ?? "",
+
+    examples: input.examples.map(e => ({
+      sentence: e.sentence,
+      highlightedLemma: input.lemma,
+      difficulty: e.difficulty ?? "medium",
+      contextTag: e.contextTag ?? "daily",
+      sourceType: "constructed"
+    })),
+
+    collocations: [],
+    
+    synonyms: (input.synonyms ?? []).map(word => ({
+      word,
+      nuance: ""
+    })),
+    
+    antonyms: [],
+
+    usageNotes: [],
+    
+    semanticRelations: {
+      hypernyms: [],
+      hyponyms: [],
+      relatedConcepts: []
+    },
+
+    etymology: {
+      origin: "",
+      evolution: ""
+    },
+
+    voiceout: {
+      ttsText: input.lemma,
+      slowTtsText: input.lemma,
+      pronunciationHint: ""
+    },
+
+    learningAids: {
+      mnemonic: "",
+      visualCue: ""
+    },
+
+    aiGrounding: {
+      allowedScope: "Only answer questions using this card's data and general linguistic knowledge.",
+      ambiguityNotes: ""
+    },
+
+    version: "1.0",
+    createdBy: "ai",
+    qualityScore: 0.85,
+    createdAt: now
+  };
+}
+
+/**
+ * Validates input data before card creation.
+ * Throws descriptive errors if validation fails.
+ * 
+ * @param input - Data to validate
+ * @throws Error if validation fails
+ */
+export function validateCardInput(input: unknown): asserts input is BaseCardInput {
+  const data = input as Partial<BaseCardInput>;
+
+  if (!data.language || typeof data.language !== "string") {
+    throw new Error("Invalid or missing language");
+  }
+
+  if (!data.lemma || typeof data.lemma !== "string") {
+    throw new Error("Invalid or missing lemma");
+  }
+
+  if (!data.partOfSpeech || typeof data.partOfSpeech !== "string") {
+    throw new Error("Invalid or missing part of speech");
+  }
+
+  if (!Array.isArray(data.definitions) || data.definitions.length === 0) {
+    throw new Error("Definitions must be a non-empty array");
+  }
+
+  if (!Array.isArray(data.examples) || data.examples.length === 0) {
+    throw new Error("Examples must be a non-empty array");
+  }
+}
+
+/**
+ * Creates multiple cards in batch from an array of inputs.
+ * Useful for bulk import operations.
+ * 
+ * @param inputs - Array of card inputs
+ * @returns Array of created cards
+ */
+export function createBaseCardBatch(inputs: BaseCardInput[]): BaseCard[] {
+  return inputs.map(input => createBaseCard(input));
+}
diff --git a/app/lib/types/card.types.ts b/app/lib/types/card.types.ts
new file mode 100644
index 0000000..95b6f63
--- /dev/null
+++ b/app/lib/types/card.types.ts
@@ -0,0 +1,114 @@
+/**
+ * Input data structure for creating base cards
+ */
+export interface BaseCardInput {
+  language: string;
+  lemma: string;
+  partOfSpeech: string;
+  definitions: Array<{
+    definition: string;
+    register?: string;
+    domain?: string;
+  }>;
+  examples: Array<{
+    sentence: string;
+    difficulty?: "easy" | "medium" | "hard";
+    contextTag?: string;
+  }>;
+  ipa?: string;
+  synonyms?: string[];
+}
+
+/**
+ * Complete base card schema
+ */
+export interface BaseCard {
+  cardId: string;
+  language: string;
+  lemma: string;
+  normalizedLemma: string;
+
+  partOfSpeech: string;
+  otherForms: string[];
+
+  phonetics: {
+    ipa: string;
+    respelling: string;
+  };
+
+  definitions: Array<{
+    definition: string;
+    register: string;
+    domain: string;
+    confidence: number;
+  }>;
+
+  coreMeaning: string;
+
+  examples: Array<{
+    sentence: string;
+    highlightedLemma: string;
+    difficulty: "easy" | "medium" | "hard";
+    contextTag: string;
+    sourceType: string;
+  }>;
+
+  collocations: Array<{
+    phrase: string;
+    context?: string;
+  }>;
+
+  synonyms: Array<{
+    word: string;
+    nuance: string;
+  }>;
+
+  antonyms: Array<{
+    word: string;
+    nuance: string;
+  }>;
+
+  usageNotes: string[];
+
+  semanticRelations: {
+    hypernyms: string[];
+    hyponyms: string[];
+    relatedConcepts: string[];
+  };
+
+  etymology: {
+    origin: string;
+    evolution: string;
+  };
+
+  voiceout: {
+    ttsText: string;
+    slowTtsText: string;
+    pronunciationHint: string;
+  };
+
+  learningAids: {
+    mnemonic: string;
+    visualCue: string;
+  };
+
+  aiGrounding: {
+    allowedScope: string;
+    ambiguityNotes: string;
+  };
+
+  version: string;
+  createdBy: string;
+  qualityScore: number;
+  createdAt: string;
+}
+
+/**
+ * User profile structure with cards
+ */
+export interface UserProfile {
+  userId: string;
+  cards: Record<string, BaseCard>;
+  updatedAt: string;
+  createdAt: string;
+}
diff --git a/app/package-lock.json b/app/package-lock.json
index 479a198..891d07b 100644
--- a/app/package-lock.json
+++ b/app/package-lock.json
@@ -64,6 +64,7 @@
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       "dev": true,
+      "peer": true,
       "dependencies": {
         "@babel/code-frame": "^7.29.0",
         "@babel/generator": "^7.29.0",
@@ -1460,6 +1461,7 @@
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       "dev": true,
+      "peer": true,
       "dependencies": {
         "csstype": "^3.2.2"
       }
@@ -1515,6 +1517,7 @@
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       "dev": true,
+      "peer": true,
       "dependencies": {
         "@typescript-eslint/scope-manager": "8.54.0",
         "@typescript-eslint/types": "8.54.0",
@@ -1983,6 +1986,7 @@
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       "dev": true,
+      "peer": true,
       "bin": {
         "acorn": "bin/acorn"
       },
@@ -2300,6 +2304,7 @@
           "url": "https://github.com/sponsors/ai"
         }
       ],
+      "peer": true,
       "dependencies": {
         "baseline-browser-mapping": "^2.9.0",
         "caniuse-lite": "^1.0.30001759",
@@ -2829,6 +2834,7 @@
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       "dev": true,
+      "peer": true,
       "dependencies": {
         "@eslint-community/eslint-utils": "^4.8.0",
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       "dev": true,
+      "peer": true,
       "dependencies": {
         "@rtsao/scc": "^1.1.0",
         "array-includes": "^3.1.9",
@@ -5038,6 +5045,7 @@
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+      "peer": true,
       "engines": {
         "node": ">=0.10.0"
       }
@@ -5046,6 +5054,7 @@
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