useless trivia: What Word Means: To Join - To Make One?

Questions

in egyptian mythology, who married two of her brothers?

in engineering, the measurement or control of equipment by fluid jet devices?

in england, what is the speaker of the house not allowed to do?

in folklore, supernatural, sea-dwelling creature with the head and upper body of a beautiful woman and the lower body of a fish?

in football, what are the white marks intersecting each five-yard line?