# Should a list of equations displayed vertically have conjunction? [closed]

Which of the following ways of writing equations is acceptable and/or preferable in mathematical typography?

\section*{Format 1}
The four equations in the computation graph are:
\begin{align*}
a_1 & = f(W_1 a_0 + b_1). \\
a_2 & = f(W_2 a_1 + b_2). \\
a_3 & = f(W_3 a_2 + b_3). \\
a_4 & = f(W_4 a_3 + b_4).
\end{align*}

\section*{Format 2}
The four equations in the computation graph are
\begin{align*}
a_1 & = f(W_1 a_0 + b_1), \\
a_2 & = f(W_2 a_1 + b_2), \\
a_3 & = f(W_3 a_2 + b_3), \\
\text{and }
a_4 & = f(W_4 a_3 + b_4).
\end{align*}

\section*{Format 3}
The four equations in the computation graph are
\begin{align*}
a_1 & = f(W_1 a_0 + b_1), \\
a_2 & = f(W_2 a_1 + b_2), \\
a_3 & = f(W_3 a_2 + b_3), \\
a_4 & = f(W_4 a_3 + b_4).
\end{align*}


Format 2 reads like it is closest to being correct English. But I think I have seen Format 3 more often in math books. Is there any consensus on which of these styles is correct and/or appropriate in professional mathematical typesetting?

Here are some related posts that I have already read but did not help me to resolve the answer to this question:

Note: I don't have any style guide I can look at to answer this question. I am writing for general audience. My PDFs may be hosted on my blog, GitHub, etc. I am trying to improve my typography style.

• Syntactically, I think both 2 and 3 are correct, not only in English but in Spanish (my native language). And maybe if I have to choose, I would go with 3, because of the conjuction "and" in 2, that to me is unnecessary in this case. And I think, personally, that "less words" is better practice in math writing. Btw, I do not know if there is an actual manual for math writing (like the Knuth's). – Cragfelt Nov 7 '17 at 5:22
• This is a stylistic question, so off-topic for the site. I'd avoid “and”, which gets completely out of place. Punctuation is optional, but one should be consistent across a document. – egreg Nov 7 '17 at 8:58