Polyptoton is the term to refer to the repetition of the same root word with various endings.
From the Les Miserables song "I Dreamed a Dream"
I dreamed a dream of days gone by.
When hope was high
And life worth living.
From Shakespeare's Sonnet 116:
Love is not love
Which alters when it alteration finds,
Or bends with the remover to remove.
From the Christmas song "You're a Mean One, Mr. Grinch":
Your heart is full of unwashed socks, your soul is full of gunk, Mr. Grinch, The three words that best describe you are as follows, and I quote, "Stink, stank, stunk"!
Prayer of St. Francis of Assisi:
Divine Master, grant that I may not so much seek to be consoled as to console;
To be understood as to understand;
To be loved as to love;
For it is in giving that we receive;
It is in pardoning that we are pardoned;
And it is in dying that we are born to eternal life."
Literary Terms Examples