Both translations of "oppassen" are very common.

1. to be careful, to look/watch out, to mind [verb] [paste op, opgepast] ['op-pa-sun']

Examples:
- "Pas op het afstapje!"
("Mind the step!")

- "Je moet oppassen dat je niet met je voet tussen de spaken komt!"
(<common warning to kids sitting on the back of mom’s bicycle:> "You have to watch out that your foot doesn’t end up between the spokes!" Literally: "…that you do not come with your foot between the spokes.")

- "Pas op met oversteken, het kan druk zijn!"
("Watch out when crossing (the street), it might be crowded!")

- "Pas nou toch op!"
("Be careful now!")

- "Pas erop dat je alle ramen sluit voordat je weggaat."
("Mind to close all windows before you leave.")

- "Oppassen!"
("Be careful! / Watch out!")

- "Pas op!"
("Be careful! / Watch out!")

Related words:
- "Uitkijken": to watch out.
- "Opletten": to pay attention.
- "Voorzichtig": careful.
- "Roekeloos": reckless.

2. to take care of, to baby-sit [verb] [paste op, opgepast] ['op-pa-sun']

Examples:
- "Marc moet vandaag oppassen op zijn achternichtje."
("Today Marc has to baby-sit his second cousin.")

- "Nou ik ga! Pas goed op je zusje hè!"
("I’m off now! Take good care of your little sister o.k.?")

- "We gaan drie weken op vakantie, maar ik heb de buren gevraagd op het huis te passen."
("We are going on holiday for three weeks, but I have asked the neighbours to watch the house.")

Related words:
- "Babysitten": to baby-sit.
- "Babysitter": baby sitter. Both verb and noun are common.

Example:
- "We gaan vanavond naar de schouwburg. Gelukkig hebben we een babysitter kunnen vinden!"
("Tonight we are going to the theatre. Luckily we have been able to find a baby sitter!")