If you're using Google Sheets and you want to count the occurrences of a certain letter or word, there's a pretty easy function that you can use.
Looking for a word and only that word
In this first set of data in the image above, we will be counting any cells that contain the word "Yellow" and only that word. To count the occurance of the word yellow in the range B2 to B9 you can use the count COUNTIF function as such:
=COUNTIF(B2:B9,"yellow"). It performs a conditional count. In this case, only if the cell or ranges of cells is equal to Yellow. Yellow is not case-sensitive so this is going to pick up three instances even though B7 is not capitalized. If the COUNTIF technique is doing everything you need, then you're done and there is no need to try anything more involved.
Looking for a word occurring anywhere a cell
In this second set of data, things will get a little bit more complicated. We are looking for a certain word that occurs anywhere in any of these cells. First, you want to use COUNTIF again and give it a range
=COUNTIF(C2:C9, "*Yellow*"). For this example, the range will be C2 to C9. If it has the word yellow and anything before which is what asterisk means, and anything after it which is the second asterisk, then it should be counted.. It just has to have yellow in some part of it. Anything can be nothing so it can start or end with yellow too. This function is also counting 3 because of the yellow plane, the yellow car, and the little yellow boat.
I hope that was helpful and now you know the formula for counting any occurrences of any word that you're looking for.