I add «ful» or «less» to make these sentences meaningful. 1) My cousin can't speak. He is speech... 2)The rainbow is colour... 3) My friend thinks a lot. He is a thought...person. 4) Our teacher is very kind. She is so help... 5) It's use...to learn your lesson by heart, you should better understand it.
1 speechless
2 colourful
3 thoughtful
4 helpful
5 useless