not always though man it's entirely situational to keep it 100
it's like when you a kid and your parents have a problem with you smoking weed.. you go kick it with the crew and tell your parents "we going to the movies" and end up going to the movies, smoking a few blunts and getting some grub... it's not a lie just cause you withheld info on the other places you went cause if that was the case you'd have to literally detail every single place you went from the second you left until the second you came back for it not to be a lie
or if your girl wants to know how she looks in the dress and she looks like Precious, but you in a relationship with her cause you think she's beautiful and will think that no matter wtf she's wearing, if you say "you look beautiful in that dress" you're not telling a lie just cause you didn't say "you look beautiful in that dress but you also look like Precious"
just cause you leave info out doesn't make it a lie unless you get asked a direct question, in that case it's best to just be tactful