I am using CCK to build a content type,"Application" with multuple fields, "application name","application description" for example. In the Application content type, basing on my understanding, there should be another content type which is "Applicant" with multiple fields, "name", "age" for example.

Instead of building a flat structured form containing both Application's and Applicant's fields, is there any way to build a relational stuctured form using CCK, which allows "Application form" to contain or reference the "Applicant form"??

Comments

Try using Inline Entity Form with Entity referene

Provides a widget for inline management (creation, modification, removal) of referenced entities.

Requires integration code to be provided for each entity type that can be referenced.
Supports the commerce_product (including Commerce AutoSKU integration) and commerce_line_item, node, taxonomy_term entity types out of the box.
Integration for other entity types has not yet been written, patches welcome.