I start this column with a confession: I was well into adulthood before I grokked that the words horizon and horizontal were intimately related — so intimately, in fact, that the one is the source of the other. There's no good excuse for this oversight: you merely have to look at the words to see that they are nearly identical. What threw me off was the stress shift. I heard and learned the words before I ever saw them, and stored them in separate memory locations. Horizon was in my lexicon as a somewhat unusual word because its sound pattern is different than a lot of other -zon words, like Amazon, Barbizon, blazon. Horizontal, meanwhile, was stored in a box with other -al words that describe spatial relations: frontal, dorsal, ventral, elliptical. For the longest time, these two memory locations clearly did not talk to each other. There's also the fact that horizon is, to me, a thing, whereas horizontal is an abstraction, and my little brain apparently didn't want to note a connection between such things. And anyway, who ever uses horizontal to talk about the horizon?

It's not the first time I was ever tripped up by English words that are not so obviously related to one of their derivatives. The reasons for this vary, but the general reason was stated clearly by H. W. Fowler, the great authority on usage, in one of his most endearing quotes. He observed that relations among words "come to us from our forefathers as an odd jumble and plainly show that the language has not been neatly constructed by a master builder who could create each part to do the exact work required of it, neither overlapped or overlapping; far from that, its parts have had to grow as they could." If such jumbles can trip up native speakers, it's no wonder that learners of English often struggle with drawing connections between related words that sound, and may even look, different.

Native speakers and learners alike can readily discern the relationship between marry and marriage. It's helpful that there's a parallel in carry and carriage, and an even more obscure one in ferry in ferriage (the business of ferrying or the fare paid therefor). But we don't find harriage to accompany harry, nor tarriage to accompany tarry. We do, however, find tarriance. So much for verb-noun connections. Regarding adjectives, it's quite a leap to descry that marital pertains to marriage, and poking about elsewhere in the lexicon we find no help, for there is no carital, harital, ferital, or tarital. And be careful that you don't misspell marital as martial, because then you're talking about war, not marriage. Mars, you'll remember, is the Roman god of war.

When I first came upon the adjective empirical I was sure that it must have something to do with empire. But wrong; the adjective for empire is imperial; empirical is separately derived from a word that means "experienced" and its meaning is "based on evidence or experience." Empirical does in fact have a related noun — the now mostly obsolete word empiric (which also serves as an adjective).

Would it be asking too much of language that cardinal and ordinal numbers resemble each other? They usually do, after a rocky beginning. Since we pick up the vocabulary of and differences between cardinal and ordinal numbers at an early age, the odd disconnect between one and first flies under the radar of things that we might question as contrary to reason; ditto for two and second. Thereafter, the English cardinals and ordinals settle into a more predictable pattern. Do learners struggle with this distinction? It probably depends on what language they're coming from. English is not alone in having apparently unrelated words for the low-value cardinals and ordinals. There's French un and premier, German ein and zuerst, Arabic واحد (wahad) and أول (ool), all of which are translations of one and first. Many languages have this odd disconnect.

But English goes one better (Yes! One!) by having some other derived words from the number one that bear a passing resemblance to the number but don't sound like it: there's only, which is really just one with the adverbial suffix -ly tacked on, and the silent e thrown out. And there's alone (originally, a mashup of all one); from it, we get both lone (a clipped version of alone) and lonely. There's probably no good excuse for overlooking the connections here. The rock group Three Dog Night reminded us, in their 1968 hit "One", that "one is the loneliest number." Literally. It's also the oneliest number.

Learners and native speakers alike may have gone down the rabbit hole of words related to hearing and words related to speech that look and sound oddly like each other. Ear, aural, and auricle all have an etymon in Latin auris, "ear". Oral and orifice have an etymon in Latin or-, os, "mouth". In many dialects of English, oral and aural have the same pronunciation. And there's the further twist that when you say aural (however you say it), you may be referring not to speech or to hearing, but to an aura, a word that is related to air. Really, it seems like you need an oracle to figure all of this out. Oracle, by the way, is not related to any of the foregoing words, but it's related to oration, which is a thing that can be both spoken or heard.

Galaxy shares an obvious quality in my lexicon with horizon: it's an unusual word because we have few other words ending in the sound /aksē/, and when we do, their stress is on the penultimate syllable: maxi, waxy, flaxy, taxi. You kind of want the adjective derived from galaxy to be galaxic, but it's not. It's galactic (note the stress shift), and if you heard these words before you ever saw them, you might easily fail to see the connection. Galaxic probably lost out because when a need arose for an adjective related to galaxy, English was already rife with Greek and Latinate adjectives ending in -ctic that have their origins in Greek words ending -κτικός and Latin words ending -i(t)cus. The more subtle clue about the connection between this pair is that they're both about milk. The galaxy that we live in, the Milky Way, supplies the English word for such swirling masses in general. γαλακτικός (galaktikos) is the Greek word for milky; the Latinate adjective is, of course, lactic.

The relations among words are not so different from those among people. It's not unusual for, say, first cousins to bear no obvious resemblance to each other, but if we examine their DNA we find that there are enough overlapping segments to confirm what the paper record tells us: they have a grandparent in common. Similarly with words: when they are introduced to us in speech their relationships are often invisible, but examination of their constituent letters and histories reveals their connection to each other.

Click here to read more articles from Language Lounge.

Orin Hargraves is an independent lexicographer and contributor to numerous dictionaries published in the US, the UK, and Europe. He is also the author of Mighty Fine Words and Smashing Expressions (Oxford), the definitive guide to British and American differences, and Slang Rules! (Merriam-Webster), a practical guide for English learners. In addition to writing the Language Lounge column, Orin also writes for the Macmillan Dictionary Blog. Click here to visit his website. Click here to read more articles by Orin Hargraves.