• 知識ちしき — knowledge
• 認識にんしき — recognition, awareness
• 意識いしき — consciousness
• 識別しきべつ — discrimination, distinction
• 常識じょうしき — common sense
• 識者しきしゃ — learned person, expert

識 is made up of 言 (speech/words) and 音符職 (ショク), which conveys meaning related to understanding and knowledge. It originally referred to recalling or recognizing things clearly through words and memory — and is now widely used in education, psychology, and communication fields.

彼かれは 知識ちしきが 豊ゆたかです。
He has a wealth of knowledge.

色いろを 識別しきべつする 能力のうりょくを 試ためします。
We’ll test your ability to distinguish colors.

The onyomi “シキ” is the only reading in modern Japanese and appears in words like 知識ちしき, 意識いしき, and 識別しきべつ. There is no common kunyomi reading.