Breakdown of Certaines formes géométriques sont des triangles.
être
to be
des
some (plural indefinite)
la forme
the fitness / the shape
certain
certain / some (certains, certaine, certaines)
Questions & Answers about Certaines formes géométriques sont des triangles.
Why use Certaines here instead of Quelques?
Why is the article des required before triangles?
Would the meaning change if certaines were placed after the noun?
Yes! When placed before the noun, certain acts as a determiner meaning "some" or "certain" (like in this sentence). When placed after the noun, it acts as an adjective meaning "sure" or "undeniable" (for example, une victoire certaine means "a sure victory").