Question: Here is one sentence: A unit of wheat is a bushel.
Here is another sentence: He was a member of a special police unit.
Does the unit mean the same thing in the two sentences?

Answer: different meanings

Question: Here is one sentence: There is no better time than now.
Here is another sentence: Now is the right time.
Does the now mean the same thing in the two sentences?

Answer: the same meaning

Question: Here is one sentence: Beat one's breast.
Here is another sentence: The eagle beat its wings and soared high into the sky.
Does the beat mean the same thing in the two sentences?

Answer: different meanings

Question: Here is one sentence: He was a great actor in his time.
Here is another sentence: The time of year for planting.
Does the time mean the same thing in the two sentences?

Answer:
the same meaning