Stress can be defined as the state of being mentally, physically and emotional disturbances due to demanding circumstances or the state of exerting pressure or tension on a particular topic or object.
It can also be expressed as a adjective.
Stressed - The state of being pressurized.
Mina is stressed after her meeting with international colleagues.
Ans 1/ word stress:-The stress placed on syllabus within words is called word/lexical stress.

Ans2/sentence stress:- The stress placed on words within sentences is called sentence/prosodic stress.
Ans 3/content word:-Content words are the words such as nouns,most verbs,adjectives and adverbs that refer to an object,action or charactereistic
Ans 4/grammatical word:-Function words (or grammatical words or synsemantic words or structure-class words) are words that have little lexical meaning or have ambiguous meaning

i am not sure this answer is correct