A chain is only as strong as its weakest link.
What does it mean?
The entry from Wikipedia about chains shows:
A chain is typically made of metal. A chain may consist of two or more links
But I didn't understand this quote about chains.
It effectively means that no matter how strong most of the chain is, even if there's one weak part, it could break the entire chain.
It means you need to eliminate all weaknesses for there to be no risk that the 'chain' could fail.
Do you understand the word "chain"? If not, look that up.
Suppose you use a chain to, say, tow some heavy object behind your truck. If the object is heavy enough, the chain might break. Where will it break? At the weakest link.
The point being this: Suppose you made a chain with 100 links, 99 links of case-hardened steel and one link of tin. Then you try to pull the heavy object with it. What will happen? The tin link will break. It doesn't matter how strong the other 99 links are. If just one link is weak, the chain will break. The overall strength of a chain is not the strength of the strongest link, or even of the average link. The overall strength of a chain is the strength of the weakest link.
This is often used as an analogy for other cases where one poorly-designed part can cause an entire machine to fail, or where one incompetent person can cause an entire organization to fail, etc. People may say, "Fred is the weakest link on our team", meaning, Fred's laziness or incompetence or whatever flaw will make the team fail no matter how well everyone else does.
A chain is only as strong as its weakest link.
It means that if you want to know the level of strength of a chain (i.e. how strong is it) then you have to check which link (chain made of links - see here) is weakest and then the level is determined by this one.
It means that even though the rest of the links in this chain are strong but anyway because one link is not strong as they are, therefore you can break this chain while you break the weakest link...
Think about a chain made of 20 links. 19 links are made of strong metal but one link is made of thin plastic. Then the strength of this chain is determined by this weak plastic link, because when you break this plastic link you actually break the chain and then the rest metal links don't really matter...
It's a metaphor that is used to compare a group of something to a chain and the impact of a single member.
If you have a chain holding something and one of the links breaks, the chain itself isn't useful anymore hence when it is used, it is comparable to saying:
A group is only as strong as its weakest member.
Chains are constructed from multiple links of (usually) metal joined together. Because of this, the strength of the chain relies upon the strength of the individual links in the chain. If you were to test the strength of the chain (e.g. by pulling on both ends simultaneously), then when the chain breaks it would generally break at a particular link. It would break at that link because it would be the weakest link in the chain. Therefore the strength of the whole chain is equivalent to the strength of the weakest link in it.
This saying has become a metaphor for the strength of any entity that is made up of multiple parts, usually that entity is a group of something, e.g. people.
Imagine you had 7 people running a race as a team, and the team had to finish together, at the same time. no matter how fast your FASTEST person is, he can not finish until EVERYONE else finishes at the same time.
Therefore the SLOWEST person on the team affects the speed of the fastest runner. The ENTIRE team is as slow as the slowest person. The slow person is the "weakest link"
Just as a chain, with individual links that can hold many tones... if one of the links can only hold 2.2 pounds, or a kilo, or whatever measurement you choose to use, the entire chain, no matter how strong, breaks when the weakest link breaks. Any single link breaking, causes everything to fail.
A chain is only as strong as it's weakest link is a metaphor. The analogy here, is of a chain where, the strength needed to break the
weakest link, is all that is needed to break the
This is a commonly used metaphor, for example:
Sam is completely out of shape. I don't want him on our volley ball team; a chain is only as strong as its weakest link.
In this example, Sam, who is out of shape could cause the team to lose in a volley ball match, being analogous to the weakest link.
If you are running a marathon, the success of the team depends on every participant. You have to run the race as if it is your last. If any member of the team is not physically fit, not agile, runs too slow and even drops the baton, the race is lost. It doesn't matter how agile the other participants are. The one that drops the baton is the weakest link