When do I use is or does when I ask a question? For example, Is your item still for sale? Does your item still for sale? I am not sure which one to use.

How it works is a phrasal noun. How does it work? is an interrogative sentence (question). The former is commonly used as a heading and there is no question mark at the end.

Does $\sum\frac {\sin n} {n}$ converge? I have tried the comparison test, root test and ratio test but still can't prove it is convergent or divergent.

Jul 28, 2021 · What do the less-than and greater-than symbols right next to each other mean? Does it mean either less than or greater than? In other words, not equal? I am trying to …

Feb 8, 2014 · In the set of real numbers, there is no negative zero. However, can you please verify if and why this is so? Is zero inherently "neutral"?

Nov 6, 2018 · The answer in both instances is 'have'. It is ungrammatical to use 'has' in questions that begin with 'Do' or 'Does'. In these types of questions the verb 'do' is conjugated based on …

What does "by" mean if we are talking about a date? Ask Question Asked 9 years, 8 months ago Modified 4 years, 10 months ago

Sep 15, 2014 · tl; dr - It's exclusive if the situation described is notable by its absence. It's likely to be inclusive if the situation described is notable by its presence. At its heart, until describes …

Nov 17, 2013 · Wiktionary lists re as a preposition that means “About, regarding, with reference to; especially in letters and documents”, while OED1 (1914) says: Re sb² [Ablative of L. res …

You say you don't understand what $\mathbb {R}^n$ means. Do you have difficulty with the real plane (ie $\mathbb {R}^2$) or real 3D space (ie $\mathbb {R}^3$) ?