"The boy put his bike against the wall" means that he positioned the bike so that that it was leaning on the wall. Perhaps the boy leant the bike with the handlebars and saddle touching the wall so that it wouldn't fall.

This is the only possible meaning of the word 'against' in this kind of context. When you are talking about physical location, against' always means 'position something in close contact with something else'. For example, "He pressed his face against the window pane and stared out" , "Hold the ice pack against your cheek".

This is a very different meaning from 'against' when you are talking about abstract ideas such as conflict or opposition, as in "Brazil are playing against Germany in the semi-final" or "He spoke out against the tax cuts".

The fact that this word can be used to express different ideas in different contexts does not present a problem for native speakers. When we're talking about physical location, we know the right word to use to talk about positioning an object in close contact with another object; when we're talking about abstract ideas, we know the right word to talk about one person or group being in opposition to another. The fact that this happens to be the "same" word is not particularly important. Note that I've put the word "same" in inverted commas: this is because it is arguably not the "same" word: it expressed a different concept, so perhaps we treat it as a "different" word on some level. Perhaps you should try to do the same?

Hi Aleksei, your question has already been answered. I just want to add, since you encouraged us to <em>talk about "against"</em>, that there is another meaning that can also relate to real things around us. It is "in visual contrast to" and can be used when talking about something you see, if there is a background.

<em>Paintings look best against a simple white wall. </em>(Cambridge Dictionary)

<em>The dark ruins of the castle stood out against the evening sky. </em>(Macmillan Dictionary)

Although in modern use learning against a wall or similar constructions have become akin to a new word, with slightly different meaning than to be opposed or against something. They are actually not two almost separate words. learning + against simply means it the wall was not there acting opposing 'gravity' the bike or the person or animal 'leaning against' the wall would fall down. It is a kind of reverse logic. = not that the wall is actually physically pushing against the bike, person or animal, but the bike, person animal is using the wall to oppose [be against] them falling down; because of the way they are leaning with gravity and the centre of balance acting against them. 'leaning against the wall'. One word many uses and in modern times, that phrase "leaning against the wall" is like a negative question except it is not a negative question but a positive statement. You, they, the man, bike, object, animal is leaning and up against the wall.

The argument holds true in all senses of the word. You would have difficulty remaining standing if you were not 'leaning - beginning to fall and (up) against the wall". If the wall were not acting against your precarious leaning stance, you would be in trouble.

The dictionary definitions of touching are just to attempt to give a simple explanation for modern usage for a very ancient word always with many uses 'again+st".

NOTE:

in modern usage you always 'lean a bike or object against a wall/door" etc to prevent it falling down. You always lean against a wall/door or table etc, to give yourself support, either to prevent falling down or to have a sort of half rest when tired,

hey Aleksei,

I don't know any Russian, but I am led to believe that Russian just like English has tons of homonyms (words that have more than one meaning). As proof I challenge you to look up random words in an English dictionary and see how many of them you can find that has only one meaning listed.

Oh, thanks a lot for your explanation, La Liseuse, now it is clear