write vs drop a line

write and drop a line both are verbs.

Word	Noun	Adjective	Verb	Adverb
write	No	No	Yes	No
drop a line	No	No	Yes	No

As verbs, write and drop a line are synonyms defined as:

write (verb)	drop a line (verb)
communicate or express by writing	contact in writing
record data on a computer
contact in writing
produce a literary work
mark or trace words or symbols on a surface
write or name the letters that comprise the conventionally accepted form of (a word or part of a word)
write music
create code, write a computer program