What are the similarities between Arabic and Hebrew?

The Semitic languages are characterised by being based on roots formed of three consonants into which different vowels are inserted to indicate different, but related words, including gramatical variants of each individual word. An English parallel would be SNG into which different vowels are inserted to produce the noun SONG and the present, past, participle forms of the corresponding verb (SING, SANG, SUNG and the obsolete YSUNG), only whereas English does this quite infrequently, the Semitic languages do it all the time.