I would like to know if there is a grammar rule(s) that defines whether a word is gramatically legal or not. I understand a word is given meaning by a human and anyone can give meaning to anything. Therefore I realize it is probably impossible to create a set of laws that can absolutely define the legality of a string of letters. Barring that extreme example, is there a practical/general set of such rules? For example, I remember my grade 2 teacher saying that if a word does not contain at the minimum 1 vowel, then it is not a legal word. Based on that principle, I might claim that the word 'lkjsdlf' is not a legal word. Is there a generally accepted set of grammatical parameters that define whether a word is legal or not (apart from looking it up in a dictionary)? The reason I'm asking this is to determine if it's possible to programmatically validate a word (rather than using a list of 100,000+ words from a dictionary). The goal is to categorize 'lkjsdlf' and ...