drop somebody a line/note

drop (one) a line

To contact someone, usually with a letter, note, or phone call. I know you'll be busy enjoying yourself, but please, drop me a line on your trip. I'll drop you a line once I get settled in at school.
See also: drop, line

drop (one) a note

To send one a letter or message. I always try to drop Janet a note around her birthday so that she knows I'm thinking of her.
See also: drop, note
Farlex Dictionary of Idioms.

drop a line

Correspond, write a short letter or note. For example, I hope you'll drop me a line soon. This idiom uses line in the sense of "a few words in writing," a usage first recorded in 1647.
See also: drop, line
The American Heritage® Dictionary of Idioms by Christine Ammer.

drop somebody a ˈline/ˈnote

(informal) write a short letter, message, etc. to somebody: I dropped her a line inviting her to my birthday party.
See also: drop, line, note, somebody
Farlex Partner Idioms Dictionary
See also:
  • drop someone a line
  • drop (one) a line
  • drop a line
  • drop a line and drop a few lines; drop a note
  • drop (one) a few lines
  • help (oneself) to
  • help to
  • keep (oneself) to (oneself)
  • keep to
  • keep yourself to yourself