∫ Integral ∮ Physical integral

In direct proportion to ...

multiplication

σ addition

∞ union

Cross point

⊥ Vertical

parallel

electric arc

circle

no less than

Not more than

Constant equality.

Integer symbol

Integral of closed graph

In direct proportion to ...

∏ Connected product is the abbreviation of multiplication of many things.

∑ is pronounced as "Sima" plus sign, which is the abbreviation of adding up many things.

∨ Take the maximum value, such as 4∨9=9.

∧ Take the smallest, such as 4∧9=4.

⊥ Vertical means that two straight lines are vertical. For example, the straight line AB is perpendicular to the straight line CD, which can be written as AB⊥CD.

‖ Parallel, that is, two straight lines are parallel. For example, the straight line AB is parallel to the straight line CD, which can be written as AB‖CD.

⌒ pronounced as "arc", such as AB on a circle, can be written as adding that symbol to AB.

The representation of a circle, for example, the center of the circle is O, can be represented as O.

I'm not sure.