1.
to avoid leaving a path, road, etc.
SYN stick to sth :
Keep to the track—the land is very boggy around here.
2.
to talk or write only about the subject that you are supposed to talk or write about :
Nothing is more irritating than people who do not keep to the point .
3.
to do what you have promised or agreed to do :
to keep to an agreement / an undertaking / a plan
4.
to stay in and not leave a particular place or position :
She's nearly 90 and mostly keeps to her room.