The number and type of particles it emits gives rise to the type of radiation being emitted. In the case of alpha decay, a helium nucleus (two protons, and two neutrons) are emitted. This is the lowest energy radiation type, but it is none the less dangerous to human health.
This abbreviation is usually found on maps, on expense reports, and it is very common to see miles abbreviated to mi. just about any time they are referenced. You might abbreviate the word miles to mi. on a road sign or a map with directions to a destination. It is also common to see such abbreviations in headlines or newspaper titles where space is a concern. Outside of maps, business mileage reports, etc. the word is not abbreviated in general prose.
Miles and nautical miles are two units used for measuring length and distances. Both have older origins compared to the SI units, and they are not consistent units. Miles. Mile, also called the statute mile or the land mile is a unit for measuring length in the imperial system of units. 1 Mile is equal to 5,280 feet or 1,760 yards. It is equal to 1609.34 meters and 1.60934 km. Before 1959, the yard was not a convention as a unit and the length of yard varied from country to country.