What is the difference between "in-line" and "inline"

Question

When I type inline on Google, I get the definition of in-line, but no indication of misspelling.

Answer 1

In the adjective sense, those are the same words as alternative spellings. The one without a hyphen is more common in computer-related cases, such as "an inline function", while the one with a hyphen is, in my experience, more common in mechanical or manufacturing situations - "in-line engine", "in-line manufacturing".

The programming and related meanings have somewhat taken on a subtle separate meaning of there own, where it refers to some element or entity that could be defined separately and referred to from other locations instead being placed where they are needed. An inline function, which I mentioned above, is one that the compiler copies into the code everywhere it is needed, rather than making a function call - which is relatively expensive at run-time - and having the code sitting in just one place, ready to be called from elsewhere. This leads to its alternate verb meaning, which only occurs without a hyphen, which refers to the process of taking something that was not originally stated to be inline and making it be so. "Inlining" is a process that compilers go through to optimise code, detecting functions that would perform better (at the cost of larger executable files) if they were made inline.

It also has a special meaning in CSS, where it refers to elements that occur in the flow of text rather than breaking the flow of text. It's naturally an adjective there, as "inline element", but elision for the sake of efficiency (or laziness) has lead to it becoming a noun. Rather than say "inline element", people just say "inline" instead.