megabytes

1. A unit of computer memory or data storage capacity equal to 1,048,576 (2²⁰) bytes.

2. One million bytes.

1. A unit of computer memory or data storage capacity equal to 1,048,576 bytes (1,024 kilobytes or 2²⁰ bytes).

2. One million bytes.

Our Living Language  : In computer science and industry usage, the prefix mega- often does not have its standard scientific meaning of 1,000,000, but refers instead to the power of two closest to 1,000,000, which is 2²⁰, or 1,048,576. The calculation of data storage capacity (measured in bytes) is based on powers of two because of the binary nature of bits (1 byte is 8, or 2³, bits). Thus, a megabyte is 1,048,576 bytes, although it is also used less technically to refer to a million bytes. Other numerical prefixes are interpreted similarly. With data transmission rates (measured in bits per second), a bit is considered as a signal pulse, and calculations are generally based on powers of ten. Thus, a rate of one megabit per second is equal to one million bits per second. However, in certain technical contexts, megabit can also refer to 1,048,576 bits. Similarly, the prefix kilo- refers to 1,000 or 2¹⁰ (1,024); giga- to 1,000,000,000 (one billion) or 2³⁰ (1,073,741,824); and tera- to 1,000,000,000,000 (one trillion) or 2⁴⁰ (1,099,511,627,776).