Adds the meaning of 'even' to a noun or noun phrase, often implying an extreme or unexpected case. Can be used with も for emphasis (さえも).
Even the teacher couldn't solve this problem.
He couldn't even write his own name.
Even a child knows that.
Used in conditional clauses (～ば/～たら + さえ) to indicate the minimum condition needed for a result. Often translates to 'if only' or 'as long as'.
If only I had money, I could do anything.
As long as the weather is good, we'll go on a picnic.
besides; on top of that; what's more
Adds an additional, often negative, element to a situation. Commonly used with に (さえに) or in the pattern ～に加えて～さえ. Implies 'not only ... but also ...'.
It's raining, and on top of that, the wind is getting stronger.
Not only was he late, but he even forgot his homework.
Many people think that as long as they have money, they can do anything.
As long as you practice every day, you'll get better.
On top of the rain, even the wind started getting stronger.
すら is a more literary and emphatic way to say 'even', often restricted to negative contexts, while さえ is the common everyday equivalent.
まで can express 'even' by showing an extreme degree reached, whereas さえ more directly marks an unexpected minimum case.
も is the neutral inclusive particle ('also, too'), while さえ adds a stronger nuance of 'even' or an extreme/unexpected example.
しかも is a conjunction meaning 'moreover, what's more' used between clauses, while さえ in this sense attaches to a noun to add an extra, often negative, element.
だけ means simply 'only', while さえ in conditional form (～ば/～たらさえ) stresses that the item mentioned is the sole sufficient condition for a result.
さえ is the plain, common particle for 'even'; でさえ adds emphasis and typically follows a noun with the copula で.
さえ is the everyday equivalent of だに and works in both positive and negative sentences, while だに is formal and almost always negative.
さえ marks a minimal or extreme example, meaning 'even', while こそ singles out an element as precisely the key point.
さえ expresses 'even' in a more formal or written register, while だって's 'even' sense is casual spoken Japanese.
The origin is uncertain, but it is a native Japanese particle with no clear kanji association.