Conlangs vs. Natural Languages: What's the Difference?

Esperanto has native speakers — children who grew up speaking it at home. Modern Hebrew was deliberately revived and expanded in the late 19th century. Meanwhile, Klingon has a grammar, a dictionary, and a translated Hamlet. So where exactly is the line between an invented language and a "real" one?

Here's how linguists draw it — and why the line keeps moving.

Quick Definitions

A natural language develops on its own through generations of use. Nobody designed English, Japanese, or Swahili. They evolved.

A constructed language (or conlang) was consciously designed by one person or a small group. Klingon, Esperanto, Dothraki, and Quenya are all conlangs.

In short: a natural language grows; a conlang is built. But once people start speaking a conlang, it starts growing too.

The Counterintuitive Truth: Every Successful Conlang Turns Natural

Here's what surprises most people. The more successful a conlang is, the less constructed it becomes.

Esperanto was published by L. L. Zamenhof in 1887 with a small, regular grammar. Today, Esperanto speakers use idioms, slang, and shortcuts Zamenhof never designed. Linguists estimate Esperanto has around 1,000 native speakers — people who learned it as a first language from their parents. Their Esperanto has quirks that behave exactly like natural language change.

We call this naturalisation drift: the moment a designed language gets enough speakers, it starts evolving on its own, and its creator loses control.

Difference 1: Regularity

Natural languages are full of exceptions. English has "go/went", "mouse/mice", "be/am/is/are/was/were". These irregulars come from centuries of sound change and borrowing.

Most conlangs start regular. Esperanto has no irregular verbs at all. But fictional conlangs often add irregularities on purpose to feel real. David J. Peterson built High Valyrian with a simulated history so its irregular forms would have "reasons." Try it in the Valyrian Translator.

Difference 2: Purpose

Conlangs are usually built for one of three reasons:

1. Auxiliary languages (auxlangs) — for international communication. Examples: Esperanto, Interlingua, Toki Pona (partly).
2. Artistic languages (artlangs) — for fiction and art. Examples: Klingon, Quenya, Dothraki.
3. Engineered languages (engelangs) — to test ideas about logic or thought. Examples: Loglan, Ithkuil.

Natural languages have no purpose in this sense. They just exist because people needed to talk.

Difference 3: Vocabulary Size

Natural languages have enormous vocabularies. The Oxford English Dictionary contains over 600,000 word forms.

Conlangs are much smaller:

• Toki Pona: about 120–140 core words, by design
• Na'vi: over 2,000 words
• Klingon: a few thousand words
• Esperanto: tens of thousands of root-derived words

Small vocabularies force creativity. In Toki Pona, a "friend" is literally a "good person" (jan pona). That constraint is the point.

Difference 4: Who Decides What's "Correct"

In natural languages, nobody is fully in charge. Dictionaries describe how people speak. Even the Académie française, which advises on French, can't stop people from saying le weekend.

In conlangs, there's often an authority:

• Marc Okrand still coins official Klingon words.
• Paul Frommer approves new Na'vi vocabulary.
• Tolkien's notes are treated as canon by Elvish scholars.

This is canon-bound grammar — rules that come from a creator rather than from speakers. It's the one feature that truly separates artistic conlangs from natural languages. But when fans fill gaps themselves (like "Neo-Sindarin" fans do with Tolkien's Sindarin), canon-bound grammar starts drifting toward natural usage.

The Blurry Middle: Revived and Planned Natural Languages

Some languages don't fit neatly into either box.

Modern Hebrew

Hebrew was used for religion and scholarship for centuries but had very few everyday speakers. Eliezer Ben-Yehuda and others revived it as a spoken language in the late 1800s, coining words for modern life. Today it has millions of native speakers. It's natural in origin but heavily engineered in its modern form.

Standardised Languages

Standard German, Standard Italian, and Standard Indonesian were all shaped by committees and writers choosing one dialect over others. They're natural languages with constructed polish.

Old English Reconstructions

When people "speak" Old English today, they reconstruct pronunciation from texts. It's a natural language brought back with modern guesswork. See what it looks like in the Old English Translator.

Can a Conlang Ever Become Fully Natural?

Linguists usually say a language becomes fully "natural" when it has a community of native speakers who pass it on across generations, changing it as they go.

By that test:

• Esperanto is closest, with native speakers into a third generation in some families.
• Klingon had one famous experiment: linguist d'Armond Speers spoke only Klingon to his son for the first few years of his life in the 1990s. The boy stopped responding to it as he grew older.
• Fictional conlangs like Dothraki and Na'vi have fluent adult learners, but no native speaker communities yet.

Where This Line Is Heading

As more children grow up surrounded by games, films, and online communities, we'll see more people learning conlangs young. We predict that within the next 20 years, at least one fictional conlang — most likely Klingon or High Valyrian — will have a small but documented community of childhood bilingual speakers. When that happens, the old distinction between "invented" and "real" will matter far less than who speaks the language, and how.

Try Them Yourself

See the difference between built and grown languages side by side:

• Klingon Translator — artistic conlang
• Valyrian Translator — artistic conlang with simulated history
• Quenya Translator — Tolkien's "Elf-Latin"
• Old English Translator — natural language, 1,000 years old
• Shakespeare Translator — natural language, 400 years old
• Pig Latin Translator — a language game, not a language