Cap,capt

(capture capable captive)

Cred

(credible,credit)

Dict

(dictation,dictionary)

Duc,duct

(induce,conductor)

fac,fact

(Artifact,facsimile,factor)

graph

(autograph,graphic,graph paper) 

log

(Dialog,biology)

Mort

(mortar,mortal,mortician)

scrib,script

(transcribe, subscript, scripture)

Spec,spect

(specimen, aspect, spectator)

tact 

(Tactical,tactile,contact)

ten

(tenacious, retentive, tentative)

therm

(thermoses,thermostat,themometer)

ver

(verify, very)