Informal spelling of through used as a preposition.

• From one side or end of something to the other.
• Via or by way of; along or across.
• Throughout a period or area.
• By means of; because of.
• Up to and including a limit in ranges.

Informal spelling of through used as an adverb.

• From one side to the other; past.
• From start to finish; completely; all the way.
• So as to reach or connect.

Informal spelling of through used as an adjective.

• Nonstop or direct, as in a thru train or ticket.
• Allowing passage, as in thru traffic or drive-thru.
• Finished or done; having reached the end.