Umahluko phakathi kweSemi-etreyila

Umahluko kwiitreyila ezipheleleyo, i-semi{0}}iitreyila zinee-asi zazo ezibekwe emva kombindi wesithuthi somxhuzulane (xa zilayishwe ngokulinganayo) kwaye zixhotyiswe ngehitch ehambisa amandla athe tye okanye athe nkqo kwitrektara. Iitreyila ezigcweleyo zinee-asi ezimbini, ngelixa ii-semi{2}}ezirhuqwayo zinenye. I-semi{4}}inqwelo erhuqwayo sisithuthi esingenawo amandla kwaye sabelana ngomthwalo waso kunye nesithuthi esikhulu, sixhomekeke kwisithuthi esikhulu ukuba siyitsale.
Ukubeka nje, itreyila epheleleyo iqhagamshelwe kwilori engaphambili nge hook. Semi-itreyila iqhagamshelwe kwivili letrektara lesihlanu ngephini lokutsala. Ilori yothutho yesikhongozeli eqhelekileyo yisemi{3}}erhuqwayo eqhelekileyo, kunye nesahlulo sokulayisha ngasemva yisemi{4}}erhuqwayo.
Zikwahluka kwindlela ezisetyenziswa ngayo. Iitreyila ezigcweleyo zisetyenziselwa ubukhulu becala-uthutho lomgama omfutshane phakathi kwefektri, amazibuko, iidokhi, iindawo zokugcina, kunye nezinye iindawo, ngelixa iitreyila ezinge--ezirhuqwayo zisetyenziselwa uthutho{3}}lomgama omde.