Adverbs in Gaelic can be formed by using the inflectional morpheme 'gu,' or can follow a preposition. However, many Adverbs in Gaelic are non-inflected, and thus occur as fixed phrases.
Formation
Adverbs with 'gu'
Largest Group, Adjvective + gu = adverb
- 
- 
| Thuirt | Seamus | ris | gu | fuar |  - 
| say-PAST | Seamus | to him | ADV | cold |  - 
| 'Seamus said coldly.' |  
 
Adverbs Formed using Prepositions
| air èiginn | 'with difficulty' | air chall | 'lost' | 
| fa sgaoil | 'in dispersed fashion' | air seòl | 'sailing' | 
| an làthair | 'present' | aur iteal | 'flying' | 
 (Lamb 2001)
Intesifiers
Adverbs can be intensified using "glè" (very), and "ro"'extremely: 
- 
- 
| mòr | → | gu mòr | → | gu glè mòr |  - 
| 'great' | → | 'greatly' | → | 'very greatly' |  
 
- 
- 
| Thuirt | Seamus | ris | gu | glè | fuar |  - 
| say-PAST | Seamus | to him | ADV | very | cold |  - 
| 'Seamus said very coldly.' |  
 
Time Adverbs
Present
| an ceart-uair | 'just now' | a-nochd | 'tonight' | 
| a-nis(d) | 'now (contrastive)' | am bliadhna | 'this year' | 
| an-dràsda | 'now' | an-diugh | 'today' | 
 (Lamb 2001)
Past
| an-dè | 'yesterday' | a-bhòn-dè | 'day before yesterday' | 
| an uiridh | 'last year' | an-raoir | 'last night' | 
| a-bhòn-raoir | 'now' | Mar-thà/Mu-thrath | 'already' | 
 (Lamb 2001)
Future
| an eara(i)r | 'day after tomorrow' | gu sìorraidh | 'for eternity' | 
| a-màireach | 'tomorrow' | an ath-bliadhna | 'next year' | 
| an ath-oidhch | 'tomorrow night' | tuilleadh | 'forever' | 
 (Lamb 2001)
Indefinite
| an còmhnaidh | 'always' | greis | 'for a while' | 
| uaireannan | 'sometimes' | fhathast | 'still/yet' | 
| uaireigin | 'sometime' | 
 (Lamb 2001)
Direction and Location
| Location | Movement | English | 
| "shuas" | "suas" | 'up' | 
| "shìos" | "sìos" | 'down' | 
| "a-bhos" | "a-nall" | 'over here | 
| "thall" | "a-null" | 'over there' | 
 (Lamb 2001)
Degree
Amplification, Emphasis, downtoning, and Hedges
Amplifiers
| gu lèir | 'completely' | 
| gu mòr | 'greatly' | 
| direach | 'exactly' | 
| glè | 'very' | 
| ro | 'extremely' | 
 (Lamb 2001)
Emphatics
| gu dearbh | 'indeed' | 
| gu deimhinne | 'with certaintly' | 
| gun teagamh | 'without a doubt' | 
 (Lamb 2001)
Downtoners
| gu ìre | 'to an extent' | 
| gu ìre bheag | 'to some extent' | 
| an ìre mhath | 'sometimes' | 
 (Lamb 2001)
Hedgess
| cha mhòr | 'almost' | 
| 's dòcha | 'perhaps' | 
| ma dh 'fhaoidte | 'perhaps' | 
 (Lamb 2001)