Definitions:

1. A grade rating a student's work as 'Incomplete'. NOUN
   • She missed a few exams, therefore the professor gave her an 'I' for the course.
2. The ninth letter of the alphabet. NOUN
   • 'I' comes after 'H'.
3. The Roman numeral for one. NOUN
   • VI=6, IV=4.
4. Used by a speaker to refer to himself or herself. NOUN
   • Jim and I are getting married.

Synonyms:

• myself
• one