An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

The logarithm with → base 10. It is known also as the → decimal logarithm, decadic logarithm, or Briggsian logarithm, after Henry Briggs, an English mathematician who pioneered its use.

→ common; → logarithm; → decimal.

→ common logarithm.

→ decimal; → logarithm.

The → exponent of the → power to which it is necessary to raise a fixed number to produce the given number. The fixed number is called the → base. The logarithm of x to the base a, denoted log_a(x), is the unique → real number  y such that a^y = x. In the familiar system of → common logarithms, the base is 10. In the system of → natural logarithms, the base is e = 2.7182818 ... (→ number e). For example, the logarithm of 100 (base 10) is 2 because 10² = 100.

Mod.L. logarithmus, coined by Scottish mathematician John Napier (1550-1617), literally "ratio-number," from Gk. logos "proportion, ratio, word," → logic + arithmos "number," → arithmetic.

Of or pertaining to a → logarithm.

→ logarithm; → -ic.

Same as → reddening coefficient.

→ logarithmic; → extinction.

A scale of measurement in which an increase of one unit represents a tenfold increase in the quantity measured (for common logarithms)

→ logarithmic; → scale.

Same as the → natural logarithm.

After John Laird Napier (1550-1617), the Scottish mathematician who invented logarithm; → logarithm.

The logarithm in which the → base is the → irrational number e = 2.718281828.... Also called → Napierian logarithm. The natural logarithm is denoted ln, an abbreviation of logarithmus naturalis. Natural logarithms are related to → common logarithms through: ln x = (1/M) log x, with M = (1/ln 10) ≅ 0.434294.

→ natural; → logarithm.