The two articles in English are a/an and the.
The word a (which becomes an when the next word begins with a vowel - a, e, i, o, u) is called the indefinite article because the noun it goes with is indefinite or general. The word the is known as the definite article and indicates a specific thing.
Fill in the gaps:
Speaking on _ visit to _ hospital, Boris Johnson refused to rule out _ UK leaving _ EU on 31 October, contradicting statements made by _ chancellor this morning. He said that Corbyn should “man up” and back _ election. No 10 suggested yesterday that _ government could go “on strike” and refuse to do anything until _ election took place but _ threat appeared to soften today. After previously insisting they would “do _ bare minimum to keep _country running”, Johnson said this afternoon: