Sentence:  Hence , when the address * * f is computed from * * f , the cell * * f and all Y-cells in its chain must be inspected to determine whether * * f is already in the form list or whether it should be <WSD>added</WSD> to the form list and the chain . 
Meaning of the word marked with <WSD> tags:  make an addition (to); join or combine or unite with others; increase the quality, quantity, size or scope of