Etymology 1 
From Old French aplier, (French appliquer), from Latin applicō (“join, fix, or attach to”); from ad + plicō (“fold, twist together”). See applicant, ply.
apply (third-person singular simple present applies, present participle applying, simple past and past participle applied)
- (transitive) To lay or place; to put or adjust (one thing to another);—with to; as, to apply the hand to the breast; to apply medicaments to a diseased part of the body.
- 1697, John Dryden, Translation of Virgil's Aeneid:
- He said, and to the sword his throat applied.
- (transitive) To put to use; to use or employ for a particular purpose, or in a particular case; to appropriate; to devote; as, to apply money to the payment of a debt.
- (transitive) To make use of, declare, or pronounce, as suitable, fitting, or relative; as, to apply the testimony to the case; to apply an epithet to a person.
- (Can we date this quote?) Milton,
- Yet God at last To Satan, first in sin, his doom applied.
- (transitive) To fix closely; to engage and employ diligently, or with attention; to attach; to incline.
- (transitive) To betake; to address; to refer;—used reflexively.
- (Can we date this quote?) Johnson,
- I applied myself to him for help.
- (intransitive) To submit oneself as a candidate for.
- I recently applied for a job as a bartender at the tavern.
- Most of the colleges she applied to were ones she thought she had a good chance of getting into.
- Many of them don't know it, but almost a third of the inmates are eligible to apply for parole or work-release programs.
- (intransitive) To pertain or be relevant to a specified individual or group.
- That rule only applies to foreigners.
Part or all of this entry has been imported from the 1913 edition of Webster’s Dictionary, which is now free of copyright and hence in the public domain. The imported definitions may be significantly out of date, and any more recent senses may be completely missing.
Derived terms 
to put to use for a purpose
to submit oneself as a candidate
to be relevant to a specified individual
Etymology 2 
apple + -y
apply (comparative more apply, superlative most apply)
- Alternative spelling of appley.