What is the average occurrence of the word "grec" on each Wikipedia page that has this word?
grec refers to word = 'grec'; AVG(occurrences where word = 'grec')
SELECT CAST(SUM(T2.occurrences) AS REAL) / COUNT(T1.wid) FROM words AS T1 INNER JOIN pages_words AS T2 ON T1.wid = T2.wid WHERE T1.word = 'grec'