External power source for arduino Nano

I have a transformer AC/DC that gives me 9V, 2A at the output. Can I use it to power an Arduino Nano?

As long as it outputs 9V DC, then yes

Adding to @UKHeliBob's reply:

Do not connect it to 5V :wink: But to Vin.
Do not try to draw significant current from the Nano's 5V and/or 3.3V pins.