"Man" can be used as a separate component in a sentence, such as "He is a very honest person", and "Man" is the head language of a noun phrase alone, so "Man" is a morpheme; And the morpheme "person";
In modern Chinese, it can not be used alone, but must be combined with other morphemes, such as democracy, people's livelihood, police, people, fishermen, etc., in order to appear as a component in the sentence, so "people" is not a morpheme.
Extended data:
Some monosyllabic morphemes can be used independently, so they can become words independently. For example, morphemes like "Man, Run, Me, La, Red ……" are called "morphemes". Others can't be used independently, so they can't become words independently. Morphemes such as "people, friends, machines ……" are called "morphemes without words". A morpheme cannot be a word alone, and it can never be a word;
A morpheme that can become a word independently cannot guarantee that it is a word at any time and any occasion. For example, the word "ren" in "ren" is not a word, but it appears here in the form of morpheme, which is a component of the word "ren" and cannot be separated or inserted with other components.
Baidu Encyclopedia-Morpheme