About this phrase

Ar is a simple preposition meaning on.

• It often lenites but there are gramatical subtleties. For example:
  • Ar bord (loinge): aboard / on board (ship).
  • Ar bhord: (physically) on a table.
• It causes eclipsis in certain phrases. For example:
  • Ar gcúl: backwards, postponed, delayed ⁊rl…

Tús is a masculine noun meaning beginning. It is eclipsed by ar.

Thus, ar dtús: at the start, for a start.

Eclipsis and capitalisation

In the written or printed form, eclipsing consonents should never be capitalised:

• Correct: Ar dTús.
• Incorrect: Ar Dtús.

Where eclipsing consonents are present in entirely capitalised text, small-caps are an acceptable compromise:

• Ar dTús.

Prepositional pronouns formed from the preposition ar

• orm: on me.
• ort: on you.
• air: on him; on it (masculine).
• uirthi: on her; on it (feminine).
• orainn: on us.
• oraibh: on ye (plural).
• orthu: on them.

The same prepositional pronouns' emphatic forms

• orm-sa: on me.
• ort-sa: on you.
• air-sean: on him; on it (masculine).
• uirthi-se: on her; on it (feminine).
• orainn-ne: on us.
• oraibh-se: on ye (plural).
• orthu-san: on them.