Alex80

is (not) an idiom (all the three cases)
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Whenever you refer to a word as to be a title of a group of things, you have to use an indefinite article (a/an).
Airbus is not a car.
Train is a vehicle. (one of the vehicles known)
Get the jump of something is not an idiom (as opposed to the 'Get the hang of sth', which is an idiom -- the latter one can be titled "IDIOM")
- When you're talking about titles - use indefinite articles
- When you're talking about things themselves - use definite articles

*excuse my pickiness