In chemistry, this is a thing.
Refers to a chemical formula, with elements and such.
It makes the mathematicians sing.
Mathematical formulas for equations!
A baby may know it as well /
but not the same way, you can tell.
There are bottle formulas for feeding to babies.
For the baby likes to think of drinks /
and mathematicians prefer the thought of thinks.
Of course, baby formula and equation formulas are quite different--one is a drink, and the other is something you think up.
Engineers use them, yes they do /
but not for trains, no to you.
Engineers do use formulas to find values, but train engineer is the term for people who handle/drive trains, so they don't use formulas to derive answers to their particular problems. (Thanks to @Mithrandir for the tip on this one!)
Einstein used an E and C
Referring to E = mc^2
the baby prefers the milk, you see. /
And in yet another way /
your mother used it, in a separate way.
Though babies may prefer their mothers' milk, mothers often use formula instead.
In the kitchen, as you may find /
but not the ones that stretch your mind.
You might find baby formula in the kitchen, but probably not a mathematical formula.
And of course, the title "Baby's drink, mathematician's think" refers to
The difference between the mix for feeding to infants, and the formulas that mathematicians find and prove.