A wye is any object shaped similar to a letter Y, especially a Y-shaped connection of three sections of road or railroad track.

A wye connection referring to electrical connections is where one end of the three coils of a three phase system are joined together and usually grounded. The three phase supply voltage is then connected to the other ends of these coils. In electrical terminology it is also known as a star connection.

Y are the homonyms for why.

A 'grounded-wye' connection describes a wye-connected supply, whose star-point (or common point) is grounded. This is essential in order to ensure stable phase voltages. I'm not sure what you mean by a 'grounded-phase' connection; if you mean a 'grounded-line' connection, then this is a short-circuit to ground from a line conductor.

A wye level is another term for a Y level, a surveyor's instrument for measuring differences of level by means of a telescope resting in a Y-shaped support.