Critical (adjective)

1. Expressing or involving an analysis of the merits and faults of something.
2. Being at a point at which a significant or decisive change occurs.
3. Being of vital importance; necessary or crucial.
4. Being in or approaching a state of crisis.
5. Being severe or severe and unfavourable in judgment or assessment.

Origin:

From middle english, from old french critique, from latin criticus ("able to discern"), from ancient greek κριτικός (kritikós, "able to discern, skilled in judging"), from κρίνω (krínō, "i separate, distinguish, judge").

Examples:

1. The critics gave the play a critical review.
2. The patient is in a critical condition.
3. It is critical that we finish this project on time.
4. The situation is critical, we must act now.
5. His critical comments hurt her feelings.