How to find words which are related morphologically?

Solution 1:

Word by letter

Type the beginning of a word and just see how many results are churned out.

ENGLISH WORDS STARTING WITH "MEDIC"

medic, medicable, medicably, medicaid, medicaids, medical, medically, medicals, medicament, medicamental, medicaments, medicant, medicare, medicares, medicaster, medicate, medicated, medicates, medicating, medication, medications, medicative, medicator, medicean, medicinable, medicinal, medicinally, medicine, medicined, medicines, medicining, medicks, medico, medicommissure, medicornu, medicornua, medicos, medics,

Your Dictionary

Has a more traditional approach but its resources are reliable; medic

Wordnet Click on any link and all will be revealed. Pretty amazing stuff, I say so myself.
medicine

Word Info has a box with the suffixes and the root word of imagination. Click on imag and imagi and a new page will open with a fair list of derivatives. imaginative

• image
  1. A reproduction of the form of a person or object, especially a sculptured likeness. etc..
• imageable (adjective)
• imageless
• imager
• imagery
• imaginable (adjective)
• imaginably
• imaginant
• Imagining
• imaginary
• imaginarily
• imaginariness
• imagination
  (list of definitions)
• imaginative
  (list of definitions)
• imaginatively
• imagine

Solution 2:

Generate Derivational Variants, Recursively

medicine|medicality|128|1|R|1|RULE|medical|medicality|$|adj|base|ity$|noun|base|dd|NounAdj| medicine|medicative|128|1|R|1|RULE|medicate|medicative|ate$|verb|base|ative$|noun|base|ddddd|NotNounAdj| medicine|medication|128|1|R|1|RULE|medic|medication|$|verb|base|ation$|noun|base|ddddd|NotNounAdj| medicine|medic|128|1|R|1|RULE|medical|medic|al$|adj|base|$|noun|base|dd|NounAdj| medicine|medicant|128|1|R|1|RULE|medic|medicant|$|verb|base|ant$|noun|base|ddddd|NotNounAdj| medicine|medicate|1024|1|R|1|RULE|medicable|medicate|able$|adj|base|ate$|verb|base|dddd|NotNounAdj| medicine|medic|1024|1|R|1|RULE|medicable|medic|able$|adj|base|$|verb|base|dddd|NotNounAdj| medicine|medicinally|2|1|R|1|RULE|medicinal|medicinally|$|adj|base|ly$|adv|base|dd|NotNounAdj| medicine|medically|2|1|R|1|RULE|medical|medically|$|adj|base|ly$|adv|base|dd|NotNounAdj| medicine|medicinal|1|1|R|1|RULE|medicine|medicinal|e$|noun|base|al$|adj|base|d|NounAdj| medicine|medicant|1|1|R|1|RULE|medic|medicant|$|verb|base|ant$|adj|base|ddddd|NotNounAdj| medicine|medical|1|1|R|1|FACT|medicine|noun|medical|adj|d|NounAdj| medicine|medicable|1|1|R|1|RULE|medic|medicable|$|noun|base|able$|adj|base|ddd|NounAdj|

The link to the java source code is provided on that page; also visit the home page. Can that help?