This is the 252nd most frequent Lithuanian word.
vaikus
"Vaikus" means "children" in English.
Here, 'vaikai' is in the nominative plural form, identifying the subject who is doing the action, which is the 'children' playing.
Vaikai žaidžia kieme.
The children are playing in the yard.
Here, 'vaikus' is used in the accusative plural form to denote the direct object of the action, referring to 'children' being taken to the park.
Moteris vedė vaikus į parką.
The woman took the children to the park.
In this sentence, 'vaikais' is used in the instrumental plural form to indicate the means or manner, implying 'with/for the children' in the action of caring.