Alignments or stone rows are groups of standing stones set in straight line. They can occur in any size group from two (usually refered to as a stone pair - see Boherboy (County Dublin)) to ten or more, although anything over four is exceptional (see Castlelanaght (County Cork)).
The function of these is a bit of a mystery, although many do seem to have significant astrological or geographical properties.
The stones making stone pairs often appear to be totally different in shape from each other, often hinting at a male and female partnership.
Standing stones, also called menhirs or monoliths, are the most simple of megalithic monuments. They are exactly what they say, a stone that stands with one end set into the ground. Being simple in form does not make them simple to understand, for they have served several purposes over time. Some were placed to mark burials, others were probably erected to mark boundaries or travel routes, the purpose of others is uncertain, but it may well have been ritual.
Standing stones can vary enormously in size from a under 1m tall to over 4m. Some have been purposely shaped (see Stone Of Destiny (County Meath)) and some must have been chosen purely for their shape (see Ballyvatheen (County Kilkenny)). Most standing stones are dated to be from the Bronze Age, but some are clearly older, especially those associated with passage tombs such as at Knowth (County Meath) and Loughcrew - Corstown (County Meath).
Others have been re-used in later times (see Kilnasaggart (County Armagh) and Breastagh (County Mayo)), perhaps to try and capture some of the powers of the old gods or to legitamise a claim to land.