This thesis deals with word formation h I Tigrinya .rnIt employs the theory of generative morpho l ogy as explainedrnin Aronoff (1976) and Scalise (1984) among others .rnAs is the case i n other Semitic l anguages , roots inrnTigrinya can be inputs for word formation and accordi nglyrnseveral nom ina l and verbal patt ern s which are formed fromrnroots are identified. The se stems/words can be the basis forrnother complex words .rnThe in puts and outputs of complex words are a l sorninvest igated. It i s argued that many sufflXes that may lookrnlike derivationals are actually non derivationals. It isrnassumed t hat the re are onl y ten der iv ation a l morphemes inrnTigrinya . The study also shows tha : suffixes o' complexrnwords are heads wherea s prefixes are non -heads. The thes isrnre v eal s that Tigr inya compl ex wores are right headed .rnMoreover, it is made clear that Ti g rinya compounds arerngenerally left headed. The y may have plural suffixes addedrnto them or the feat ure [Tbrok en plural J perco l ated f rom themrnto the whole compound.