only Definition

only
adj

1. Without any others of the same type.

Thesaurus: lone, sole, single, exclusive, unique, individual.
2. Said of someone: having no brothers or sisters.
3. colloq
Best.
Example: Flying is the only way to travel

adverb

1. Not more than; just.

Thesaurus: just, merely, barely, hardly.
2. Alone; solely.

Thesaurus: exclusively, solely; individually, singly.
3. Not longer ago than; not until.

Example: only a minute ago
4. Merely; with no other result than.

Example: I arrived only to find he had already left

conj

1. But; however.

Example: Come if you want to, only don't complain if you're bored
2. If it were not for the fact that.

Example: I'd come too, only I know I'd slow you down

Idiom: if only

I wish.
Example: If only you could be on time for once

Idiom: only too

Very; extremely.
Example: only too ready to help

Etymology: Anglo-Saxon anlic.