SC sc

When this group of two letters (or digraph, if you prefer) comes before "i" or "e", it represents the consonant we find in Eng. "shoe, show, issue"... Examples: "scimmia, scivolo, scena, scelta" ( ape, slide, scene, choice).

The same sound is represented by "sci" followed by another vowel: "sciame, sciocco, asciutto"... ( swarm, silly, dry). In this case, the "i" is silent - the first syllable of "sciocco" is quite similar to Eng. "shock" and second syllable of "asciutto" is not very different from Eng. "shoot".

Before "a, o, u, h", "sc" corresponds to [sk]: "scala, scolaro, scudo, schema, boschi"... ( stairs, schoolboy, shield, scheme, woods...).

Notice that "boschi" is the pl. of "bosco" - the "h" is inserted before "i" in order to retain the [sk] pronunciation.

The pair: Eng. scheme - It. schema can be very helpful to remember this rule.

Another "classical" pair is Aeschylus - Eschilo.