"A" is used before nouns (things, people, places or emotions) to define something.
"A mota é bonita."
"Á": is used to accentuate the stressed syllable of a word (it is never used alone).
água, árvore
"À": implies a direction or action
"Maria vai à igreja."
(it is always used alone except when the merger with articles or pronouns).
às (a + as)
àquele (a + aquele)
àquela (a + aquela)
àqueles (a + aqueles)
àquelas (a + aquelas)
àquilo (a + aquilo)
"Há" is a form of indicative (3rd person singular) of the verb haver. This word has several meanings and one of the ways we are sure that it is the verb form, is replace it with a synonym, such as "existe".
Ele disse que há/ à um acento na palavra
Ele disse que existe um acento na palavra = Ele disse que há um acento na palavra.
The example tries to demonstrate that it is possible to replace the word by the verb "existir", we learn that we should use the form of the verb haver, "há".
The verb "haver" is very interesting.
<em>Present</em>
There is = Há
There are = Há
<em>Past</em>
There was = Havia
There were = Havia
<em>Future</em>
There will be = Haverá
Examples
There was a car in front of my house.
<em>Havia um carro em frente à minha casa.</em>
There was a period where people had to work hard.
<em>Houve um período onde as pessoas tinham que trabalham duro.</em>
There were several bikes in the supermarket.
<em>Havia muitas bicicletas no supermercado.</em>
There is a good way to learn English.
<em>Há uma boa forma de aprender inglês.</em>
Ana Cristina, thank you for your explanation of the usage of the verb HAVER. As you did it in English you maybe could mention the similarity between Portuguese HÁ and English THERE IS and THERE ARE . English speaking people would, probably, understand it easier.
Regards. Kamenko
