The Spanish verb 'decir' (meaning 'to say' or 'to tell') comes directly from the Latin verb 'dicere', which had the same meaning. This is a straightforward inheritance where the Latin '-icere' ending evolved into '-ecir' in Spanish, following regular sound changes that occurred as Latin developed into Spanish. This verb is one of the fundamental communication verbs in Spanish, just as it was in Latin.

Several common Spanish words are derived from 'decir', including 'dicho' (saying, proverb), 'dictado' (dictation), and 'bendecir' (to bless, literally 'to speak well of'). The past participle 'dicho' (said) maintains the 'i' from the Latin root, while the main verb form changed to 'e'.

Many English words share the same Latin root 'dicere', including 'dictate', 'dictionary', 'dictum', 'predict', and 'contradict'. All these words maintain the core meaning of speaking or saying something. For example, to 'dictate' is to say something that others should write down or follow, while a 'dictionary' is a book that 'tells' us the meanings of words. The 'dict' element in these English words preserves the 'i' from the original Latin, while Spanish changed it to 'e' in 'decir'.