The study of the word that 'flexes', changing meaning. This study is very useful in understanding how word parts change the 'character' and also the meaning of the speech. In fact, generally every word has a 'root' and a 'ending'. For example, the termination '-o' in a verb generally indicates that it is the first person speaking. Or the termination: '-ino' indicates that something is small. If there is a '-oso' termination at the end of the word, this indicates that it is almost always an adjective, and the termination in '-a' in a noun generally indicates feminine gender