What does "ad hoc" mean?

Question

What does ad hoc mean? What is its usage? –Hong, Vietnam

Answer

Ad hoc is a word that originally comes from Latin and means “for this” or "for this situation." In current American English it is used to describe something that has been formed or used for a special and immediate purpose, without previous planning.

Ad hoc can be used as an adjective or an adverb. It is used more often as an adjective, especially in these expressions: 

• ad hoc committee
• ad hoc group
• ad hoc basis

Below are some example sentences with ad hoc that help illustrate its meaning:

ad hoc used as an adjective

• The mayor appointed an ad hoc committee to study the project.
• We had to make some ad hoc changes to the plans. 
• We'll hire more staff on an ad hoc basis.

ad hoc used as an adverb 

• The decisions were made ad hoc.

I hope this helps.