You can replace whole words only, and avoid replacing parts of words, by enabling the Find whole words only editing option. Turnsheet editing options are generally named in the same way as Microsoft Word's Find and Replace options.
Global editing options for all columns/rows can be set by clicking the Editing Options button in the turnsheet toolbar.
Editing options for individual columns/rows can be set as follows:
In a Merge Mode turnsheet, editing options can be set through the edit column dialog for the relevant column and are shared by all editing instructions created from the column.
In a Find & Replace turnsheet, the editing options for each editing instruction can be accessed from the expanded row pop-out which is the grey expand button which appears near the row number.
To check the editing options of a column/row quickly, just hover your mouse over it until a tooltip appears displaying the current settings.
Example
Document:
drag dragon
Instruction:
1. Find what: drag
Replace with: wag
Find whole words only: Yes
2. Find what: drag
Replace with: wag
Find whole words only: No
Note: In a Merge workflow, "Find what:" is your column heading, and "Replace with:" is the row content.
Result:
1. wag dragon
2. wag wagon