Formulae for the line-of-sight and transverse comoving distances, proper
motion distance, angular diameter distance, luminosity distance, k-correction,
distance modulus, comoving volume, lookback time, age, and object intersection
probability are all given, some with justifications. Some attempt is made to
rationalize disparate terminologies, or at least abuse bad usage.Comment: This short and purely pedagogical text is not submitted anywhere but
here. Errors reported to the author will be rewarded with gratitude and
acknowledgement