Confused by Shitai


I read the following sentence today on an easy news web site:

これからはいつも１０秒より速く走ることが **できるようにしたいです**

I've had a look online for an explanation of the end (in bold). I understand
that overall it means **want to** , but I can't get my head around what
function です serves here. To me it reads:

"want in order to be able to (run faster than 10 seconds) **is** ".  
Is this purely to mark the sentence as polite?




Yes, it's purely a grammatical mark of politeness.

Grammatically speaking, したい (and all other ～たい forms) is an い-adjective, so it
takes the same forms as any other い-adjective.

So in plain form:

> それは赤い。 "It is red."  
>  それはしたい。 "I want to do it."

And in polite form:

> それは赤いです。 "It is red."  
>  それはしたいです。 "I want to do it."

In both cases, the です doesn't add anything to the meaning (the verbal meaning
is already part of the adjective form), it just makes the sentence polite.
This is perhaps a little clearer in the past tense:

> それは赤かった(です)。 "It was red."  
>  それはしたかった(です)。 "I wanted to do it."




Yes, it's purely a grammatical mark of politeness.

Grammatically speaking, したい (and all other ～たい forms) is an い-adjective, so it
takes the same forms as any other い-adjective.

So in plain form:

> それは赤い。 "It is red."  
>  それはしたい。 "I want to do it."

And in polite form:

> それは赤いです。 "It is red."  
>  それはしたいです。 "I want to do it."

In both cases, the です doesn't add anything to the meaning (the verbal meaning
is already part of the adjective form), it just makes the sentence polite.
This is perhaps a little clearer in the past tense:

> それは赤かった(です)。 "It was red."  
>  それはしたかった(です)。 "I wanted to do it."

