Which vs. That: How to Choose

• In a defining clause, use that.
• In non-defining clauses, use which.

• Remember, which is as disposable as a sandwich bag. If you can remove the clause without destroying the meaning of the sentence, the clause is nonessential and you can use which.

People use which and that every day. Just because these words are common doesn’t mean they’re easy to use. In particular, clauses cause a lot of confusion, but there’s an easy way to remember which one to choose.

Which vs. That: What’s the Difference in Usage?
To understand when to use that or which, it’s important to understand clauses. A defining clause (also called an essential clause or a restrictive clause) gives information essential to the meaning of the sentence. That is used in defining clauses. Here’s an example:
My bike that has a broken seat is in the garage.

In this sentence, you understand that the speaker has at least one other bike. Specifically, the bike he’s talking about is distinguished from his other bikes by its broken seat. If you removed the clause “that has a broken seat,” you would lose the implication that he owns more than one bicycle, and even if you somehow knew about the other bikes, you wouldn’t know which one was in the garage.
Which introduces non-defining clauses. Unlike defining clauses, non-defining clauses (also called nonessential or nonrestrictive clauses) don’t limit the meaning of the sentence. You might lose interesting details if you remove them, but the meaning of the sentence wouldn’t change. Sometimes, these phrases are set off by commas.
My bike, which has a broken seat, is in the garage.
Here, the broken seat is simply a description of the bike in the garage. There’s no implication that the speaker owns more than one bike. Do you see the difference? Perhaps a little mnemonic device will help you to remember how to choose between that or which.

Which and that are common words, but they are important. By identifying your clauses as defining or non-defining, you can easily remember when to use which and when to use that. If you are ready to learn more, study up on defining and non-defining clauses.

by
Srini

Usage of Upon and Yet with examples

Upon

… upon… used to emphasize that there is a large number or amount of somethingmile upon mile of dusty roadthousands upon thousands of letters

The preposition upon is generally much more formal than on but can be used to replace it in certain situations.

It can be used instead of on after several common verbs, such as happen, depend, insist and congratulate. Examples are ‘He insisted upon seeing you even though I told him you were busy’, ‘A police patrolhappened upon the robbers as they were running out of the bank’ and  ‘My whole future depended upon the decision of one manager’.

Upon is also used to mean ‘immediately after’, as in ‘Upon his release from prison, Davis went immediately to his mother’s house’. It can also mean ‘happening soon’ and in this case it is not normally replaceable with on, as in ‘Christmas is almost upon us again’ and ‘It’s June already and the exams will soon be uponus’.
When used between two nouns that are the same, upon emphasizes the large number or amount of the thing that has been mentioned, as in ‘I’ve written to you year upon year but I have never received a reply’ and ‘They drove for days across mile upon mile of open desert’.

Upon is also used in a small number of phrasal verbs, notably set, put and chance. Set upon is often passive and means ‘attack’, as in ‘He was walking through the park when he was set upon by a gang of youths’. If you feel put upon, you feel exploited because you are doing all the work while others relax. If youchance upon (or chance on) someone or something you come across them or it unexpectedly, as in ‘I was browsing in a second-hand bookshop when I chanced upon a rare first edition’.


Yet
adverb
1. Yet means at this time, up to now or at a future time.

conjunction
1. Yet is defined as nevertheless or but.





Examples:
He is my worst enemy, and yet, I admire him as the wisest man in the world.

It requires the labor of thousands to make a pencil, and yet they are so inexpensive as to be almost free.

Yet as powerful as this concept is, it has a logical limit.

And yet, I remain very optimistic.

The boy was only four years old, and the girl was not yet six.