2. Represents the two-point product of two dyadic vectors, for example, ab times cd equals the product of A and C times the product of B and D. ..

3. Colon is a punctuation mark. It usually means a pause after a prompt or a prompt below or above, which is divided into Chinese and English half-width colons and full-width colons. There was no colon in the sentence of reading symbols in ancient China. The form and usage of the colon in the current punctuation marks are imported from the west, while the name is ideographic and original. The word "Mao" means "hidden" and "comprehensive".