diff --git a/www/apps/book/app/learn/fundamentals/data-models/relationships/page.mdx b/www/apps/book/app/learn/fundamentals/data-models/relationships/page.mdx
index c154bd812c..b3e4eca729 100644
--- a/www/apps/book/app/learn/fundamentals/data-models/relationships/page.mdx
+++ b/www/apps/book/app/learn/fundamentals/data-models/relationships/page.mdx
@@ -32,7 +32,7 @@ A one-to-one relationship indicates that one record of a data model belongs to o
 
 To define a one-to-one relationship, create relationship properties in the data models using the following methods:
 
-1. `hasOne`: indicates that the model has one records of the specified model.
+1. `hasOne`: indicates that the model has one record of the specified model.
 2. `belongsTo`: indicates that the model belongs to one record of the specified model.
 
 For example:
@@ -61,13 +61,38 @@ const Email = model.define("email", {
 
 In the example above, a user has one email, and an email belongs to one user.
 
-The `hasOne` and `belongsTo` methods accept a function as a first parameter. The function returns the associated data model.
+The `hasOne` and `belongsTo` methods accept a function as the first parameter. The function returns the associated data model.
 
 The `belongsTo` method also requires passing as a second parameter an object with the property `mappedBy`. Its value is the name of the relationship property in the other data model.
 
 ### Optional Relationship
 
-To make the relationship optional on the `hasOne` or `belongsTo` side, use the `nullable` method on either properties as explained in [this chapter](../configure-properties/page.mdx#nullable-property).
+To make the relationship optional on the `hasOne` or `belongsTo` side, use the `nullable` method on either property as explained in [this chapter](../configure-properties/page.mdx#nullable-property).
+
+### One-sided One-to-One Relationship
+
+If the one-to-one relationship is only defined on one side, pass `undefined` to the `mappedBy` property in the `belongsTo` method.
+
+For example:
+
+export const oneToOneUndefinedHighlights = [
+  ["10", "undefined", "Pass `undefined` since the relationship is only defined on the `Email` data model."]
+]
+
+```ts highlights={oneToOneUndefinedHighlights}
+import { model } from "@medusajs/framework/utils"
+
+const User = model.define("user", {
+  id: model.id().primaryKey(),
+})
+
+const Email = model.define("email", {
+  id: model.id().primaryKey(),
+  user: model.belongsTo(() => User, {
+    mappedBy: undefined,
+  }),
+})
+```
 
 ### One-to-One Relationship in the Database
 
@@ -86,13 +111,13 @@ A one-to-many relationship indicates that one record of a data model has many re
 
 To define a one-to-many relationship, create relationship properties in the data models using the following methods:
 
-1. `hasMany`: indicates that the model has more than one records of the specified model.
+1. `hasMany`: indicates that the model has more than one record of the specified model.
 2. `belongsTo`: indicates that the model belongs to one record of the specified model.
 
 For example:
 
 export const oneToManyHighlights = [
-  ["5", "hasMany", "A store has many products"],
+  ["5", "hasMany", "A store has many products."],
   ["10", "belongsTo", "A product has one store."],
   ["11", `"products"`, "The relationship's name in the `Store` data model."]
 ]
@@ -132,7 +157,7 @@ When you generate the migrations of data models that have a one-to-many relation
 
 ## Many-to-Many Relationship
 
-A many-to-many relationship indicates that many records of a data model can be associated to many records of another data model.
+A many-to-many relationship indicates that many records of a data model can be associated with many records of another data model.
 
 To define a many-to-many relationship, create relationship properties in the data models using the `manyToMany` method.
 
@@ -169,19 +194,19 @@ The `manyToMany` method accepts two parameters:
 1. A function that returns the associated data model.
 2. An object of optional configuration. Only one of the data models in the relation can define the `pivotTable`, `joinColumn`, and `inverseJoinColumn` configurations, and it's considered the owner data model. The object can accept the following properties:
     - `mappedBy`: The name of the relationship property in the other data model. If not set, the property's name is inferred from the associated data model's name.
-    - `pivotTable`: The name of the pivot table created in the database for the many-to-many relation. If not set, the pivot table is inferred by combining the names of the data models' tables in alphabetical order, seperating them by `_`, and pluralizing the last name. For example, `order_products`.
+    - `pivotTable`: The name of the pivot table created in the database for the many-to-many relation. If not set, the pivot table is inferred by combining the names of the data models' tables in alphabetical order, separating them by `_`, and pluralizing the last name. For example, `order_products`.
     - `joinColumn`: The name of the column in the pivot table that points to the owner model's primary key.
     - `inverseJoinColumn`: The name of the column in the pivot table that points to the owned model's primary key.
 
 <Note>
 
-The `pivotTable`, `joinColumn`, and `inverseJoinColumn` property are only available after [Medusa v2.0.7](https://github.com/medusajs/medusa/releases/tag/v2.0.7).
+The `pivotTable`, `joinColumn`, and `inverseJoinColumn` properties are only available after [Medusa v2.0.7](https://github.com/medusajs/medusa/releases/tag/v2.0.7).
 
 </Note>
 
 <Note>
 
-Following [Medusa v2.1.0](https://github.com/medusajs/medusa/releases/tag/v2.1.0), if `pivotTable`, `joinColumn`, and `inverseJoinColumn` aren't specified on either models, the owner is decided based on alphabetical order. So, in the example above, the `Order` data model would be the owner.
+Following [Medusa v2.1.0](https://github.com/medusajs/medusa/releases/tag/v2.1.0), if `pivotTable`, `joinColumn`, and `inverseJoinColumn` aren't specified on either model, the owner is decided based on alphabetical order. So, in the example above, the `Order` data model would be the owner.
 
 </Note>
 
@@ -189,7 +214,7 @@ In this example, an order is associated with many products, and a product is ass
 
 ### Many-to-Many Relationship in the Database
 
-When you generate the migrations of data models that have a many-to-many relationship, the migration adds a new pivot table. Its name is either the name you specify in the `pivotTable` configuration, or the inferred name combining the names of the data models' tables in alphabetical order, seperating them by `_`, and pluralizing the last name. For example, `order_products`.
+When you generate the migrations of data models that have a many-to-many relationship, the migration adds a new pivot table. Its name is either the name you specify in the `pivotTable` configuration or the inferred name combining the names of the data models' tables in alphabetical order, separating them by `_`, and pluralizing the last name. For example, `order_products`.
 
 The pivot table has a column with the name `{data_model}_id` for each of the data model's tables. It also has foreign keys on each of these columns to their respective tables.
 
@@ -257,7 +282,7 @@ The `OrderProduct` model defines, aside from the ID, the following properties:
 
 The relationship property methods accept as a second parameter an object of options. The `mappedBy` property defines the name of the relationship in the other data model.
 
-This is useful if the relationship property’s name is different than that of the associated data model.
+This is useful if the relationship property’s name is different from that of the associated data model.
 
 As seen in previous examples, the `mappedBy` option is required for the `belongsTo` method.
 
diff --git a/www/apps/book/generated/edit-dates.mjs b/www/apps/book/generated/edit-dates.mjs
index fde77bd707..fccc038bb3 100644
--- a/www/apps/book/generated/edit-dates.mjs
+++ b/www/apps/book/generated/edit-dates.mjs
@@ -41,7 +41,7 @@ export const generatedEditDates = {
   "app/learn/fundamentals/data-models/manage-relationships/page.mdx": "2024-12-12T14:23:26.254Z",
   "app/learn/fundamentals/modules/remote-query/page.mdx": "2024-07-21T21:20:24+02:00",
   "app/learn/fundamentals/modules/options/page.mdx": "2025-01-16T09:21:38.244Z",
-  "app/learn/fundamentals/data-models/relationships/page.mdx": "2024-12-12T14:08:50.686Z",
+  "app/learn/fundamentals/data-models/relationships/page.mdx": "2025-02-03T08:01:18.094Z",
   "app/learn/fundamentals/workflows/compensation-function/page.mdx": "2024-12-06T14:34:50.384Z",
   "app/learn/fundamentals/modules/service-factory/page.mdx": "2024-10-21T13:30:21.371Z",
   "app/learn/fundamentals/data-models/primary-key/page.mdx": "2024-10-21T13:30:21.368Z",