of or relating to tones or sounds; specifically (phon.), applied to, or distingshing, a speech sound made with tone unmixed and undimmed by obstruction, such sounds, namely, the vowels and diphthongs, being so called by dr. james rush (1833) " from their forming the purest and most plastic material of intonation."-of or pertaining to tension; increasing tension; hence, increasing strength; as, tonic power.-increasing strength, or the tone of the animal system; obviating the effects of debility, and restoring healthy functions.-a tonic element or letter; a vowel or a diphthong.-the key tone, or first tone of any scale.-a medicine that increases the strength, and gives vigor of action to the system.