1. Create a list of common words, the more the better. Let's say we list a common spelling dictionary of 80,000 words. 2. Create an order-5 permutation of the

1. Create a list of common words, the more the better. Let's say we list a common spelling dictionary of 80,000 words. 2. Create an order-5 permutation of the list (a result in which the order of the words matters). For an 80,000 word dictionary, that's 3.27 x 10^24 test sentences, each of five words. 3. Scan the result sentence set, using a heuristic able to distinguish valid sentences from invalid ones. Let's say that one optimized validation test requires one millisecond -- in that case, the test would require 1.04 x 10^14 years, 7536 times the age of the universe. Meaning this is a much easier question to ask than answer. EDIT: Another approach is to make an arbitrary assumption about the structure of a five-word sentence, like pronoun-noun-noun-verb-noun: "The calico cat ate breakfast.". Crude and limited, and many apparently valid results will be meaningless, but it makes the estimate easier. We realize that random words have a probability of being pronouns, nouns or verbs, pp, pn and pv. The probability of producing a valid sentence (pvs) using the described template is therefore: pvs = pp * pn * pn * pv * pn Just generate the probability values by scanning a dictionary, identifying the word types (easier said than done), perform the above equation, and you have your answer.