Q: Does the word "guard" mean the same thing in "Guard against infection." and "Guard against becoming too friendly with the staff."?

A: the same meaning

Q: Does the word "light" mean the same thing in "Put that light out!" and "The light of my life."?

A: different meanings

Q: Does the word "tea" mean the same thing in "Tea has fragrant white flowers." and "We met at the Dean's tea for newcomers."?

A: different meanings

Q: Does the word "series" mean the same thing in "A comedy series." and "His coin collection included the complete series of Indian-head pennies."?

A:
different meanings