The most difficult phrases riddles

Literally, “versus” means "in the direction of". The word is often erroneously used in English for "against", probably as the truncation of "adversus"

A blue moon is an additional full moon that appears in a subdivision of a year: either the third of four full moons in a season, or a second full moon in a month. Owing to the rarity of a blue moon, happens every two to three years, the term is used colloquially to mean a rare event, as in the phrase "once in a blue moon".

The phrase has been used to describe certain global empires that were so extensive that there was always at least one part of their territory that was in daylight. It was originally coined for the Spanish Empire, mainly in the 16th and 17th centuries. In more recent times, it was used for the British Empire, which in early 20th century has reached a territorial size larger than that of any other empire in history.

“Exampli gratia” is Latin for "given example”. This abbreviation is commonly used in many European languages.

The term is today used for handbooks, but a “vademecum” may be any helpful thing one carries around.

This famous phrase was the title of Roman Emperors.

Midas, according to a Greek myth, was once one of the judges in a musical contest between Apollo and Pan (in another version: Marsyas). The victory was awarded to Apollo, and all but one agreed with the judgment. Midas questioned the justice of the award, so Apollo caused his ears to become the ears of a donkey.

“Per capita” is commonly used in the field of statistics in place of saying "per person”.

This famous phrase is a motto of medicine. Most probably, it is a paraphrase of Hippocrates’ words.