TI, SI, and CI are used to spell /sh/ in words of Latin origin.
If you're trying to figure out how to spell the "sh" sound, here are a few pointers:
SH is used to spell /sh/ only at the beginning of a word or at the end of a syllable. The only exception is the ending -SHIP, such as in friendSHIP.
TI, SI, and CI are only used at the beginning of a syllable other than the first one. Often a base word or related word can help the speller select the right spelling. Examples:
- FACIAL uses CI; there is a C before the silent final E in FACE.
- DISCUSSION uses SI; DISCUSS ends in S.
- OPERATION uses TI, there is a T before the silent final E in OPERATE.
CH can also say /sh/. Its most common sound is /ch/, as in MUCH. Its second most common sound is /k/ in words of Greek origin, like CHRIS, SCHOOL, ANCHOR, and TECHNOLOGY. Its third most common sound is /sh/ and appears in words of French origin, like CHEF, MICHELLE, and CHAMPAGNE.
English is commonly regarded as being full of exceptions. For many generations, students have been taught incomplete "rules" which often work in only 50% of cases. It's no wonder so many students, parents and teachers grow frustrated. But, thankfully, there is a compact set of spelling rules and phonograms that explain 98% of English words. It's a delightfully rich and robust code, and can be a platform for students to practice critical thinking skills - especially those logical/literal learners who so often feel lost when their observant minds hunger for answers that so many reading programs aren't providing.
I am always delighted help pass on the code and provide resources for students and instructors. I would welcome the opportunity to work with you.