trigram

前缀

后缀

tri-: Three. · (chemistry) Used for the digit three to form systematic element names of elements whose existence has been predicted, and which have not yet been given a trivial name.
-gram: Something written, drawn or otherwise recorded. · A star polygon, with the number of outward/convex vertices (i.e.: points) indicated by the numeral prefix.

From tri- +‎ -gram, literally “three marks”.

1(linguistics) A trigraph, a sequence of three letters representing one phoneme.
2(computational linguistics) An n-gram consisting of three items from a sequence.
3(divination) Any of the eight combinations of three complete or broken