to build up: to increase slowly, to make stronger gradually Examples of TO BUILD UP They certainly have built up a vibrant user community in a short period of time. These deficits have been built up over the past 10 years and nobody said a peep.  

to put off: to postpone Examples of PUT OF The procrastinating student decided to put off doing his homework until the last minute. The Judge decided to put off reaching a decision until he’d thought about what he heard.

to keep in touch with: to maintain contact with (also: to stay in touch with) Examples of TO KEEP IN TOUCH WITH Good managers are people you keep in touch with even after you leave a position. Once the Thanksgiving holiday passes, I promise to get in touch with all of you.

to be into: to have an interest, particularly a study or style Examples of TO BE INTO Lily is into health foods; in fact, she has become a vegetarian. Harry was really into astrology a lot last year. Is he still interested in the zodiac?

at heart: basically, fundamentally Examples of AT HEART Do they actually have any interest at heart other than their own self adoration? She had their best interests at heart and acted like a surrogate mother to them.

to know by sight: to recognize Examples of TO KNOW BY SIGHT I had a look around but as Jarrod’s Dad is the only one I know by sight it was a bit of a forlorn hope. If everybody doesn’t know everybody by name they’ll certainly know each other by sight.