Your mum asks if you've done your homework. You say, "Yeah, I did the maths." That part is true. What you don't mention is the English essay you haven't started, the one due tomorrow. You didn't actually lie — every word you said was true. You just left out the part that would have got you sent upstairs to work. Your mum nods and lets you carry on playing. You technically told the truth. But you also know exactly what she was really asking, and exactly what you let her believe. There's a difference between what you said and what you did.