Q.is my lilac going to bloom next year because i trimmed the tips of its branches last year?
last year i trimmed my lilac tips shortly after its flowers were gone. This year it didn’t bloom. Is it going to bloom next year?

As long as you trim lilac before July 4th, you won't remove next year's blooms. Why your lilac didn't bloom this year is a separate matter, I believe. Lilacs can get tall and rangy so pruning is necessary. Removing just the outer parts to contain size is taking out flower-producing young wood. Instead, control the size by annually removing 1/3 of the largest branches to the ground. This technique allows more light and air penetration which helps new growth and decreases powdery mildew. Thin out crowded new shoots, especially those under pencil width. This controls overall size and keeps the shrub full of flower-producing stems. Lilacs are also subject to buds freezing when an early spring warm spells is followed by the return of cold weather. It will flower best in full sun. Make sure to keep it watered through the hot, dry days of summer and into fall. If it dries out, the buds may wither. Putting compost under the plant annually will help maintain proper nutrients and healthy soil.