I think that she will go to their ceilidh

Saoilidh mi gun tèid i dhan chèilidh aca

When making plans, we often link sentences, 'I think  (that)  I'll go'. In A1 of SpeakGaelic we saw linking with gun and  nach and how these changed tha and bha to bheil and robh .

Tha mi a’ smaoineachadh gu bheil mi sgìth
I think that I am tired
Tha mi an dòchas gu bheil i nas fheàrr
I hope that she is better

But how do we link  other verbs in the future tense?

We use gun (positive) and nach (negative) before the dependent future form of the verb. With most verbs, this is the command form:

rach! (go!)  
thèid cha tèid tèid 
 ... gun tèid… that will go
 ... nach tèid… that will not go
faigh! (get!)  
gheibh chan fhaigh faigh 
 gum faigh… that will get
 ... nach fhaigh… that will not get
faic! (see!)  
chì chan fhaic faic 
 … gum faic… that will see
 ... nach fhaic… that will not see
dèan! (make!/do!)  
cha dèan dèan 
 ... gun dèan… that will do/make
 ... nach dèan… that will not do/make
thoir! (give!/take!/bring!)  
bheircha toirtoir 
 ... gun toir… that will give …
 ... nach toir… that will not give/take/bring
thig! (come!)  
thig cha tig tig 
 ... gun tig… that will come
 ... nach tig… that will not come
Saoilidh mi gun tèid Raonaid dhan chèilidh aca.
I think that Rachel will go to their ceilidh
Saoilidh mi nach tèid Raonaid dhan chèilidh aca.
I think that Rachel will not go to their ceilidh
A bheil thu a' smaoineachadh gum faigh sinn duais?
Do you think that we will get a prize?
A bheil thu a' smaoineachadh nach fhaigh sinn duais?
Do you think that we will not get a prize?
Nach eil iad a' smaoineachadh gun tig an tagsaidh?
Aren't they thinking the taxi will come?
Tha iad a' smaoineachadh nach tig an tagsaidh.
They are thinking the taxi will not come.
Chan eil mi 'n dùil gum bi an t-aiseag dheth an-diugh.
I don't expect the ferry to be off.
Tha mi 'n dùil nach bi an t-aiseag dheth an-diugh.
I expect the ferry won't be off today.
Tha sinn an dòchas gun toir i an t-airgead dhuinn.
We hope that she will give us the money.
Tha iad an dòchas nach toir i an t-airgead dhuinn.
They hope that she will not give us the money.

Just as bha changed to gun robh or nach robh in order to link, all verbs use their dependent form with gun and nach . This is the same form used in direct questions and negatives. We’ve already come across the dependent form of irregular verbs, which need to be learned individually.

Shaoil mi gun deach i dhan chèilidh aca.
I thought that she went to their ceilidh.
rach! (go!)  
chaidh cha deach deach 
 ... gun deach… that went
 ... nach deach… that didn't go
faigh! (get!)  
fhuair cha d' fhuair d' fhuair 
 ... gun d' fhuair… that got
 ... nach d' fhuair… that didn't get
faic! (see!)  
chunnaic chan fhaca faca 
 … gum faca… that saw
 ... nach fhaca… that didn't see
dèan! (make!/do!)  
rinn cha do rinn do rinn 
 ... gun do rinn… that did/made
 ... nach do rinn… that didn't do/make
thoir! (give!/take!/bring!)  
thug cha tug tug 
 ... gun tug… that gave
 ... nach tug… that didn't give/take/bring
thig! (come!)  
thàinig cha tàinig tàinig 
 ... gun tàinig… that came
 ... nach tàinig… that didn't come

If all that is too much information, have a look at this video clip where Joy explains it for us.