Using the need to get new clothes as an example, here are five different ways to express the need.
Using the verb: ‘Caith’
Example: Caithfidh mé éadaí nua a cheannach (I need to/must buy new clothes).
Caith generally carries meanings such as ‘to spend’, ‘to throw’, and ‘to wear’, but when conjugated in the future tense, it often expresses an obligation.
Using prepositional pronouns
A need can be expressed using the verb ‘Bí’ with the prepositional pronoun ‘orm’ [‘ar’ + ‘mé’]. For example, Tá orm éadaí nua a cheannach (I need to buy new clothes).
Using the verb: ‘Bí’
This can also be used with the construct ‘de dhíth’ and the prepositional pronoun ‘orm’ to indicate a need.
For example, Tá seaicéad nua de dhíth orm (I need a new jacket).
Using ‘Is gá’
This also uses a form of the Copula (Is) with the noun gá and the prepositional pronoun ‘dom’ [do + mé]. For example, Is gá dom scairf a cheannach (I have to buy a scarf). You can read more about the Copula in my in-depth piece here.
Use the negative form ‘ní’
Speaking of the Copula, you can also use the negative form of it to express a need. For example, the present tense negative form of the copula is ‘Ní’ and you can write: Ní mór dom bróga nua a cheannach. (I need to/must buy new shoes).