A dictionary of Confusable Phrases: More Than 10,000 Idioms and Collocations

fiery words • hot words
fiery words —said of an ardent, passionate address, speech,
etc.: Bert really inspired the crowd into action with his fiery
words at the rally.
hot words —words spoken in anger; a heated argument: He
accused Valenti of drinking on the job, and after some hot
words he sent Valenti home.
fifth wheel • third wheel
fifth wheel —said of a person or thing that is superfluous or
needless: Look guys, I don’t know what’s going on, but I feel
like a fifth wheel here. I should go.
Note: 
The expression does not correlate in meaning with the
phrase fifth quarter—
1
. the summer quarter of studies: In the
fifth quarter the student is encouraged to take no more than
one course besides the four hours of thesis. 2. (dated butcher’s
term) the hide and fat of a slaughtered animal: He claimed, and
obtained the fifth quarter of the beef, as it is called (the hide
and tallow) for his forbearance.
third wheel —a third person to accompany a couple (with
the implication that one is intruding on a couple): I find it tiring
to be the third wheel, having to constantly walk behind a cou-
ple holding hand.
Note: 
The expression does not correlate in meaning with the
phrase third rail—(U.S. coll.) a subject considered by politicians
to be too controversial or dangerous to discuss: The conventional
wisdom has long been that Social Security is the third rail of
American politics.
fight for something • fight over something
fight for something —
1
. struggle to defend smth.: My Dad
says we’ll all have to fight for our country when Der Tag comes.
That’s German for the Day. 2. try in a determined way to get
or achieve smth.: Having fought for the prize so long, Gordon
is destined to find in it only disappointment.
fight over something —
1
. struggle for the ownership of smth.:
They were too apt to go to law and fight over their lands and
fishing rights. 2. argue or struggle over an issue: The First
World War was fought over a small thing. A mere scrap of
paper.