To count the number of specific words or keywords that appear in a given cell, you can use a formula based on the SEARCH, ISNUMBER, and SUMPRODUCT functions. In the example shown, the formula in C5 is:
=SUMPRODUCT(--...

Note: these is an experimental formula that uses a hard coded array constant, set down here for reference and comment. Casually tested only, so take care if you use or adapt.
Sometimes you encounter data that mixes...

To test a cell for one of several strings, and return a custom result for the first match found, you can use an INDEX / MATCH formula based on the SEARCH function. In the example shown, the formula in C5 is:
{=INDEX(...

To filter data in case-sensitive way, you can use the FILTER function with help together with the EXACT function. In the example shown, the formula in F5 is:
=FILTER(B5:D15,EXACT(B5:B15,"RED"))
Which...

To count cells that do not contain many different strings, you can use a rather complex formula based on the MMULT function. In the example shown, the formula in F5 is:
{=SUM(1-(MMULT(--(ISNUMBER(SEARCH(TRANSPOSE(...

To test a cell to see if it contains one of many strings, you can use a formula based on the SEARCH, ISNUMBER and SUMPRODUCT functions. The formula in C5, copied down, is:
=SUMPRODUCT(--ISNUMBER(SEARCH(things,B5)))...

To count cells that contain either one value or another, you an either use a helper column then tally up the count, or a more complex single cell formula.
Background
When you count cells with "OR" criteria, you need...

To categorize text using keywords with a "contains" match, you can use the SEARCH function, with help from INDEX and MATCH. In the example shown, the formula in C5 is:
{=INDEX(categories,MATCH(TRUE,ISNUMBER(SEARCH(...

To disallow input that contains one of many things, you can use a custom data validation rule based the SEARCH function.
In the example shown, the data validation applied to B5:B11 is:
=SUMPRODUCT(--ISNUMBER(SEARCH(...

To test a cell for one of many strings, while excluding others, you can use a formula based on the SEARCH, ISNUMBER, and SUMPRODUCT functions. In the example shown the formula in C5 is:
=(SUMPRODUCT(--ISNUMBER(SEARCH(...

To use XLOOKUP to match values that contain specific text, you can use wildcards and concatenation. In the example shown, the formula in F5 is:
=XLOOKUP("*"&E5&"*",code,quantity,"no...

To allow only values that contain a specific text string, you can use data validation with a custom formula based on the FIND and ISNUMBER functions. In the example shown, the data validation applied to C5:C9 is:
=...

To filter data to include only records where a column is equal to one of many values, you can use the FILTER function together with the ISNUMBER function and MATCH function. In the example shown, the formula in F5 is...

To test a range for numbers, you can use a formula based on the ISNUMBER and SUMPRODUCT functions. In the example shown, the formula in G5 is:
=SUMPRODUCT(--ISNUMBER(C5:C9))>0
How this formula works
Working from...

To check if a cell contains specific text, you can use the SEARCH function together with the ISNUMBER function. In the generic version, substring is the specific text you are looking for, and text represents text in the...