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.
The word "curve" can function as both a noun and a verb. As a noun, it refers to a smooth, continuous line that bends without angles. As a verb, it means to bend or shape something into a curve. The part of speech depends on how it is used in a sentence.
A projectile has minimum speed at the top of the trajectory.
part of speech
The part of speech for this particular word is a noun.
The part of speech for "answer" is a noun.
adverb
what part of speech is beneath
The part of speech for "explicit" is an adjective.
The part of speech for "twirl" is a verb.
The part of speech for "unfamiliar" is an adjective.
The part of speech of "came" is a verb.
The part of speech for "lecturer" is a noun.
The part of speech for "indefinite" is an adjective.