Everyone knows <b>, <i>, <a>, and <code>. But HTML has a whole second cast of inline elements that most developers go entire careers without typing once — <ins>, <dfn>, <abbr>, <var>, <q>, <mark>. Not because they're broken or deprecated. They're rare because the use cases are genuinely narrow, and when one does come up, the reflex is to reach for a <span class="something"> instead.
I bumped into this building out a prose/content section for a UI system — once you start styling text properly, you notice how many real semantic elements you'd been ignoring. So here's the whole forgotten cast, in a single sentence that legitimately uses eleven of them:
Here's what that actually is:
<p>
The experiment revealed <mark>a significant energy spike</mark> in
the reactor core. Previous readings of
<del>42.7 terawatts</del> were revised to
<ins>51.3 terawatts</ins> after recalibration. The formula
<var>E</var> = <var>mc</var><sup>2</sup> governs the conversion,
where H<sub>2</sub>O serves as the coolant medium.
<abbr title="Void Energy Reactor Interface">VERI</abbr> logs
confirm the anomaly. As Dr. Vasquez noted,
<q>the readings exceed all theoretical models</q>
(<cite>Void Research Quarterly</cite>). This phenomenon, known as
<dfn>energy cascade</dfn>, occurs when containment thresholds are
breached. The <s>original safety protocols</s> have since been
replaced.
</p>
The cast, and where you'd actually use each
Edits and corrections. <ins> and <del> are added and removed content — they pair up for change tracking, and both accept datetime and cite attributes so the edit is machine-readable. <s> is the one people conflate with <del>: it marks content that's no longer accurate or relevant (a stale price, an outdated claim), which is a different statement than "this was deleted." Two elements exist precisely because those mean different things.
Notation. <sub> and <sup> are for cases where the position carries meaning — chemical formulas (H₂O), exponents (I²R), ordinals, footnote markers — not for "make it small and raised." <var> is a variable in math or code, which is why P, I, and R above are each wrapped in one.
Reference and meaning. <mark> is a relevance highlight — it's literally what search engines use to highlight your query in the results. <abbr title="…"> gives an abbreviation its expansion, surfaced as a tooltip. <dfn> marks the one spot where a term is defined (its introducing instance, not every later mention). <cite> is the title of a work — a book, paper, album — and notably not a person's name, which is the thing nearly everyone gets wrong. And <q> is an inline quotation where the browser inserts the quotation marks for you: correct for the document's language, and correctly nested if you put a quote inside a quote. You never type a " again.
Why bother
Every one of these throws a bit of meaning into the page that a styled <span> silently discards. Screen readers announce them. <q> localizes its punctuation. <abbr> exposes the long form. <ins>/<del> are a real, parseable changelog. A <span class="highlight"> looks the same and means nothing.
The only honest reason to avoid them is that the browser defaults are inconsistent and, frankly, ugly — <mark> is highlighter-yellow, <q>'s marks are whatever, half of them are unstyled. But that's a few lines of CSS, not a law of physics. Give <mark> a brand-tinted background, <ins> a green underline, <abbr> a dotted one, <q> colored quote marks, <dfn> an italic weight — and suddenly an entire sentence of semantic richness reads as clean, deliberate typography.
Most of these you'll reach for maybe once a year. But once a year correctly — with the meaning intact and the styling handled — beats a <span> that's lying about what it is.
