Three letter rule poets such as John Milton alternated between short and long forms for function words, depending on whether they occurred on or off the meter. For instance: While many function words have more than two letters ("and", "she", "were", "therefore", etc.), the exceptions to the rule are rather two-letter content words. Only a few of these occur commonly in most texts: the words "go" (which also has a functional usage in the idiom "going to do something"), "ox" and, especially in American texts, "ax". English grammar is relatively flexible about converting words of one class to another, allowing verbal uses such
Longest words If conjugated forms are allowed, even longer real words can be made. Allowing derivatives and clitics allows the already lengthy word to grow even longer, although the usability of the word starts to degrade. Because Finnish uses free forming of composite words, new words can even be formed during a conversation. One can add nouns after each other without breaking grammar rules. If one allows artificial constructs as well as using clitics and conjugated forms, one can create even longer words: such as (102 letters), which was created by Artturi Kannisto. The longest non-compound (a single stem with prefixes and