Ayin, in contrast to Samech, is not rare. The ancients liked this guttural. Naomi נָעֳמִי and Boaz בֹּעַז both have ayin in their name. Also Orpah עָרְפָּה. It also begins some common prepositions and words.If one was to include ayin in the grammatical team, it would be a strong player and bring in the heavy usage of the two character prepositions, עַל and עִם
Many verses repeat in these exercises - it is a reading game. If one actually reads all these posts here and on Bob's Log - (click the links to the letter by letter series on the sidebars) - one will begin to recognize both form and word in Hebrew. There is no substitute for repetition - it builds ze little grey cell connections. (Actually some of those cells might be green.)
Distinguish the differing words in the following verses. There are enough examples to learn all sorts of pronomial and personal suffixes.
BDB P 768 as if alone and in one's own consciousness whether of knowledge or memory or purpose.