Q:

How to delete rows which contain less than 75 characters (about 10 words) in a particular column

SQL Server 2008 - I have a table with 10 columns and many rows in which i want to delete with a condition like delete all rows which are in particular column those are less than 75 characters (about 10 words)

A:

The easiest solution is to use the SQL function called len used like this: len(nameOffield)
In your case simply add the function to you where clause in the delete command like this:
DELETE FROM yourTableName where len(aParticularColumn) < 75

Update to answer: if your aParticularColumn is of datatype text or ntext you can use DATALENGTH instead of len. In this case it would be 
DELETE FROM yourTableName where DATALENGTH(aParticularColumn) < 75

Microsoft Documentation to the DATALENGTH function

