- tachycardiaA rapid resting heart rate, especially one above 100 beats per minute; palpitations.
- isotachAn isoline linking places on a map which have equal wind speed.
- tachydidaxyA short or rapid method of instructing; speed teaching.
- tachyhydriteAn evaporite, consisting of a mixed calcium and magnesium chloride, with the chemical formula CaMg₂Cl₆·12H₂O.