1. (noun) a natural opening in something

• micropyle
• pore
• stoma
• stomate
• pupil

2. (noun) an man-made opening; usually small

• embouchure
• mouthpiece
• mouthpiece

1. (noun) a device that controls amount of light admitted

• regulator

2. (noun) a natural opening in something

• hole

3. (noun) an man-made opening; usually small

• opening