radfahren
to ride a bike
To move around by bicycle.
Am Wochenende fahren wir oft im Park rad.
On weekends, we often ride our bikes in the park.

to ride a bike
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to ride a bike
To move around by bicycle.
Am Wochenende fahren wir oft im Park rad.
On weekends, we often ride our bikes in the park.

The verb is made up of 'Rad' (short for 'Fahrrad', bicycle) and 'fahren' (to drive/ride). So the meaning is literally 'to ride with the bike'.
Bei gutem Wetter fahre ich mit dem Rad zur Arbeit.
When the weather is good, I ride my bike to work.
Since 'radfahren' (to ride a bike) describes movement from one place to another, the perfect tense is always formed with the auxiliary verb 'sein' (to be).
Wir sind am Sonntag drei Stunden durch den Wald radgefahren.
We rode our bikes through the forest for three hours on Sunday.
'Radfahren' (to ride a bike) is a separable verb. In a main clause, the prefix 'rad' comes at the end. It is also often written as the combination 'Rad fahren', in which case 'Rad' is capitalized as a noun.
Jeden Morgen fahre ich eine halbe Stunde rad.
Every morning I ride my bike for half an hour.
to drive / ride
'fahren' and 'radfahren' can both mean that you move by vehicle. 'fahren' is the general word and fits many means of transport, for example cars, buses, trains, or bicycles. 'radfahren' is more specific and always means: to ride a bike. So you can say 'Ich fahre zur Arbeit' (I'm going to work) if it is clear what you are going by. If the bicycle is important, 'radfahren' sounds more precise and natural.

Meine Mutter fährt am Wochenende gern Rad, wenn das Wetter gut ist.
My mother likes riding her bike on weekends when the weather is good.
Sie fährt jeden Morgen mit dem Bus zur Schule.
She takes the bus to school every morning.