The Mongolian Instrumental Case: By, With, and In a Language

One ending for six English prepositions

English spreads the idea of using something across a small crowd of words. You travel by train. You build a table out of wood. You speak in Mongolian. You send a letter through a colleague. You work as a doctor. You pay in silver. Mongolian covers all six with one ending, and the ending goes on the back of the noun instead of standing in front of it.

That ending is the instrumental. Laid out morpheme by morpheme, a sentence with it looks like this:

• Бид онгоцоор ирсэн.
• we plane-INS come-PAST
• "We came by plane."

There is no word for by anywhere in that sentence. What English carries in a preposition standing free is carried here by three letters welded onto онгоц (aeroplane). Once you accept that trade, the instrumental becomes one of the most comfortable cases in the language to use: the range of meanings is wide but coherent, and almost all the difficulty is in writing the right four letters.

The four written forms

The instrumental is –аар, –оор, –ээр, –өөр — four spellings of one ending. The vowels already in the stem decide which of the four you write. Ten endings in the language come in exactly these four shapes, and the single table that sets all ten side by side is The Four-Form Suffix Table; the rule that drives the choice is on Mongolian Vowel Harmony: The Rule. What belongs here is what the ending means, and what the four shapes look like on real words.

Read down the third column and the shape is almost always obvious: the stem's own vowel comes back doubled, then р. That is the whole ending. The two exceptions are у and ү, which have no doubled form of their own and borrow the а and э ones — hence автобусаар and not a form in уу. An English speaker's instinct is to look for something that sounds like a preposition and to leave the noun alone; here the noun is where all the work happens, and nothing is added in front of it.

Where the ending meets the stem

Because the ending begins with a vowel, the join is not always clean, and three spelling adjustments show up in the forms on this page: a linking г in хөдөөгөөр, ойгоор, таксигаар and хугацаагаар; a vowel that disappears in өдрөөр, утсаар, нутгаар and галт тэргээр; and и written in place of a final ь in мориор. None of this is the instrumental's doing — the same three things happen before other endings that begin with a vowel, and the rules behind them, along with the reason only тэрэг and never галт changes in галт тэргээр, are on How a Mongolian Word Is Built: Stem Plus Suffixes. They are listed here only so that the forms in the rest of this page do not look like exceptions to what you have just read.

The vehicle

This is the use you will need first and most often, because it answers a question travellers ask every day.

• Би онгоцоор уржигдар ирсэн. (I came by plane the day before yesterday.)
• Бид маргааш галт тэргээр явна. (We leave by train tomorrow.)
• Бид машинаар Ховд аймаг хүртэл явна. (We will go by car as far as Khovd province.)

English chooses between by, on and in here according to the vehicle — by train, on horseback, in a car — and gets the choice wrong-footed by learners of English all the time. Mongolian has nothing to choose. Автобусаар, таксигаар, мориор, онгоцоор: one ending, whatever you are sitting on.

The material

What a thing is made of takes the same ending, and the English counterpart is out of or of:

• Би модоор ширээ хийсэн. (I made a table out of wood.)

The same goes for торгоор (in silk, out of silk) and for мөнгөөр, which covers both the metal and the money. Мөнгө means silver and it means cash, so мөнгөөр can be the material of a bowl or the means of a payment, and only the sentence tells you which.

The language you speak in

Here Mongolian and English part company in a way worth memorising. English treats a language as a container: you speak in Mongolian, you write in Russian. Mongolian treats it as a tool — you speak by means of Mongolian — and uses the instrumental.

• Та францаар ярьдаг уу? (Do you speak French?)
• Миний гэргий монголоор сайн ярьж байна. (My wife speaks Mongolian well.)
• Би оросоор ярьмаар байна. (I want to speak Russian.)

Three things follow from this. The name of the language carries the ending, not the verb. There is no separate word for in. And the bare nominative монгол is not an answer to "what language do you speak" — it names the people and the country, and without the ending the sentence says nothing about speaking.

The person you act through

When a person is the channel rather than the companion, that person takes the instrumental. This is the English by of "sent by courier" and "helped by my neighbour", and it is where the case is at its least intuitive for an English speaker, because the same English word with would be wrong in the Mongolian.

• Би Дэлгэрмаагаар захиа явуулсан. (I had a letter sent by Delgermaa.)
• Та хэнээр туслуулсан бэ? (By whom were you helped?)

Both verbs there carry a causative suffix, which is treated on Causative, Passive and Cooperative Verbs in Mongolian. The point for this page is the noun: Delgermaa did not come along, she was the means, and the ending says so. Reference grammars put it compactly — the instrumental of an inanimate noun gives a tool, a means, a payment, a material or a span of time, and the instrumental of an animate noun gives the agent through whom something happened.

The route, the stretch, the span

A third family of meanings has no neat English equivalent at all. The ending can mark the ground you cover rather than a destination:

• хөдөөгөөр (around the countryside, across the country)
• ойгоор (through the forest)
• нутгаар (over the home territory)

English needs around, through, across or over here and the choice is idiomatic. Mongolian makes no choice. The same logic stretches to time, where the ending gives an extent rather than a point: өдрөөр (in a matter of days), хэдий хугацаагаар (for how long, over what period). A point in time, by contrast, is not the instrumental's business; the starting point belongs to the ablative and the plain location to the dative-locative.

Working as something

One more use will surprise you, and it is common:

• Тэр эмчээр ажилладаг. (He works as a doctor.)

English as looks like a comparison word, so learners reach for something else. Mongolian reads the job as the capacity through which the work is done, and so the instrumental is the natural ending. Эмчтэй ажилладаг, with the other "with" ending, would say he works alongside a doctor — a different fact about his life.

Asking "by what?"

Because the ending covers means, route and manner, the question word takes it too. Юу (what) becomes юугаар, with the linking г you already know:

• Та юугаар энд ирсэн бэ? (How did you get here?)

Word for word that is "you by-what here came?". It is not asking why you came or who you came with; it is asking what you travelled on. The question particle is бэ rather than уу, because a question word always pulls бэ or вэ — a rule that lives on Mongolian Question Particles. The same frame produces ямар чиглэлээр (in what field, along what line).

Which "with"? And which "by"?

English with does two unrelated jobs and Mongolian uses a different ending for each. This is the single most useful table on the page.

One sentence from the method settles the distinction better than any rule, because it uses both endings at once:

• Би мориор түүнтэй хамт явсан.
• I horse-INS he-COM together go-PAST
• "I went with him on horseback."

The horse is the means, so мориор. He is the company, so түүнтэй. English says "with" twice and hides the difference; Mongolian writes it. The other ending, its three forms and the verbs that insist on it are on The Mongolian Comitative, and the source-and-comparison ending on The Mongolian Ablative. The one test that will not fail you: if you could replace the English word with "using", write the instrumental.

The same ending on a verb

The instrumental does not only land on nouns. Put it on a verb form and you get the same idea of means, now applied to an action — явснаар, from явсан (gone), is "by going, through having gone". And the combination –саар plus байна describes something that started earlier and is still running at the moment you speak:

• Бороо орсоор байна. (It has been raining, and still is.)
• Би түүнийг хүлээсээр байна. (I have been waiting for him.)

English reaches for the present perfect continuous here, which is why the pair is worth recognising early. The use of this form to chain one clause to the next — "while", "keeping on" — belongs to Mongolian Converbs.

One last thing to recognise rather than study: a handful of everyday words are frozen instrumentals that no longer feel like case forms at all, among them зүгээр (it's fine, never mind) and биеэрээ (in person), as in Би биеэрээ ирнэ (I will come in person).