1. (General Engineering) tungsten-electrode inert gas welding: a method of welding in which the arc is maintained by a tungsten electrode and shielded from the access of air by an inert gas. Compare MIG welding.
A prescription for a controlled drug is valid for 28 days from the date given on the prescription. usually six months unless it's a controlled i.e. morphine, pethidine and methadone. These medicines are often misused, so have stricter legal controls on their supply to prevent them being obtained illegally. A prescription for a controlled drug is valid for 28 days from the date given on the prescription.
This prescription is usually valid for two years, unless the optometrist recommends otherwise. This prescription can be used for prescription lenses at the optometrist or optician's practice, or taken elsewhere. The prescription will contain abbreviations and jargon, such as SPH, CYL and VA.