An acronym that stands for Microwave Amplification by Stimulated Emission of Radiation. In the field of time and frequency, the term is generally associated with the hydrogen maser.

**Maximum Time Interval Error (MTIE)**

A metric used to estimate the largest peak-to-peak variation in a digital signal. MTIE can help detect sudden frequency or phase changes that cause data loss on a communications channel.

A unit of frequency that represents one million cycles per second (10^{6} Hz).

An acronym for Microcomputer-Compensated Crystal Oscillator. An MCXO is a quartz oscillator that uses digital techniques to observe the frequency drift, and compensates for this drift through digital-to-analog conversion to a tuning port in the circuit. The stability of a MCXO is generally better than that of a TCXO, but worse than that of an OCXO.

An astronomical time scale that is based on the average length of the day, called the mean solar day. The length of an average day is different from a true or apparent solar day, due to daily variations, over the span of a year, in the Sun's apparent angular speed across the sky when viewed by an observer on Earth. For example, in a true apparent solar time scale, noon is the instant when the Sun transits the local meridian and reaches its highest point in the sky. However, the Sun is at this point at a different time each day, varying over the course of a year from 14.2 minutes ahead of noon to 16.3 minutes behind it. Thus, the length of an average or mean solar day is used for a more uniform system of timekeeping.

A unit of time that represents one millionth of a second (10^{-6} s).

A unit of time that represents one thousandth of a second (10^{-3} s).

**Modified Allan Deviation (MDEV)**

A modified version of the Allan deviation statistic. Like the “normal” Allan deviation it is used to estimate frequency stability, but has the advantage of being able to distinguish between white and flicker phase noise. This makes it more suitable for estimating short-term stability than the normal Allan Deviation.