I am trying to write a simple formula to count how many times a particular name appears in a column. I am using COUNTIF as it is a pretty straight forward process but I cannot work out how to make it happen for a name in particular. This is the case:

The column named Age will display cells with one or more names, separated by commas in case there are more than one value. Putting "Young" as an example is easy to tell the COUNTIF formula to give me the number representing how many times this word appears, either being the only value in cell or as a part of a cell with a longer string value by giving the formula the "Young" statement.
The problem comes when I want the formula to count how many times "Mature" appears in my column. I cannot work out the way to make it count only when it says "Mature" without also taking all the "Early_Mature" or "Semi_Mature"
I know this is easy for whoever knows the basics of Excel so I don't think there is need to give more details.
Thanks
