The word trajectory is a noun. The plural form is trajectories.
noun
Circumference is a noun.
"Ellipse" is a noun.
Quadrilateral can be used as a noun and an adjective.
"Curved" refers to something that deviates from a straight line. It may refer to a bend in the road, a line on a graph, or the trajectory of a baseball.
A projectile has minimum speed at the top of the trajectory.
The part of speech for this particular word is a noun.
part of speech
The part of speech for "answer" is a noun.
adverb
what part of speech is beneath
The part of speech for "unfamiliar" is an adjective.
The part of speech of "came" is a verb.
The part of speech for "twirl" is a verb.
The part of speech for "explicit" is an adjective.
The part of speech for "indefinite" is an adjective.
The part of speech for "lecturer" is a noun.