The form asks if I am the principal applicant. What is a principal applicant?
If you, or your family, are applying for B-1, B-2, or B1/B2 visas, you are all considered principal applicants, and each of you should select that box.
Applicants in the E, F, H, I, J, L, M, O, P, or R visa categories may have a principal applicant as well as what is called derivative applicants. Derivative applicants are the spouse and/or children under the age of 21 of a person applying for an employment type (E, H, I, L, O, P, R), exchange (J), or student (F, M) visa, as listed above. These spouse and child (derivative) applicants should answer “no” to this question and provide the requested information for the principal applicant (the spouse or parent).