rar
rare
Rare, not occurring often, or hard to find.
Solche gut erhaltenen Münzen aus der Römerzeit sind extrem rar.
Such well-preserved coins from the Roman period are extremely rare.

rare
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rare
Rare, not occurring often, or hard to find.
Solche gut erhaltenen Münzen aus der Römerzeit sind extrem rar.
Such well-preserved coins from the Roman period are extremely rare.

The word 'rar' (rare) is often used for especially valuable, sought-after, or unique things. It sounds somewhat more elegant or elevated.
Eine solche Begabung ist wirklich rar.
Such a talent is truly rare.
'Rar' (rare) is frequently used with nouns such as 'Exemplare' (specimens/copies), 'Fähigkeiten' (abilities), 'Güter' (goods), or 'Talente' (talents) to emphasize their rarity.
Das Museum besitzt einige sehr rare Exemplare alter Handschriften.
The museum owns some very rare specimens of old manuscripts.
The phrase 'sich rar machen' (to make oneself scarce) means that someone deliberately shows up only rarely and avoids contact. It is a reflexive construction in which the reflexive pronoun is adjusted to the person.
Du machst dich in letzter Zeit ganz schön rar, ich habe dich ewig nicht gesehen!
You've been making yourself pretty scarce lately; I haven't seen you in ages!
frequent
'häufig' and 'rar' form a clear contrast. You use 'häufig' when something happens often or occurs often. 'rar' means that something is rare or hard to find. So 'häufig' fits things or events that you experience again and again. 'rar' is more suitable for things, opportunities, or people that you only rarely see or find.

Freie Termine bei Frau Richter sind vor dem Wochenende rar.
Available appointments with Ms. Richter are rare before the weekend.
Beim Training haben wir häufig kurze Pausen gemacht.
During training, we frequently took short breaks.