Learn Hardcore Russian: Я иду через лес.

Иду is the 1st person singular present tense of идти (to go on foot) in a single direction. It can be translated as I go (habitual) or I am going (right now); in this sentence it means I am going at this moment.

Why use иду instead of хожу or ездить?

Russian has pairs of motion verbs:

идти versus ходить both mean “to walk.” Идти indicates unidirectional motion (one-way, right now), whereas ходить indicates multidirectional or habitual motion (regularly going back and forth).
ездить means “to go by vehicle.”
Since the speaker is walking through the forest on a single trip, иду is the correct choice.

Why do we say через лес and what case does через require?

Через means through or across and always governs the accusative case. It implies movement entering on one side of something and exiting on the other. Therefore лес appears in the accusative.

Why doesn’t лес change its ending in the accusative?

Лес is a masculine, singular, inanimate noun. In Russian, inanimate masculine nouns have identical forms in the nominative and accusative cases, so лес stays unchanged.

How is через лес different from в лес?

В лес (with в
- accusative) means “into the forest” (motion toward the inside).
Через лес means “through the forest” (entering one side, exiting the other).
They express different spatial relations.

Can you omit Я in Я иду через лес? What changes?

Yes. Russian often drops subject pronouns because the verb ending already indicates the subject. Иду через лес still means I am going through the forest. Including Я adds emphasis or clarity but isn’t grammatically required.

Could you use сквозь or по instead of через? How would the meaning change?

Сквозь лес also means through the forest, but is more formal or literary.
По лесу (with по
- dative) means around/in the forest, focusing on wandering inside rather than traversing from side to side.
  Each preposition adds its own nuance.

If you want to talk about the future, why not say Я пойду через лес instead of иду?

Пойду is the perfective future of идти and means I will go (action as a complete event in the future). Иду is present and describes what’s happening now. If you want to emphasize a future ongoing action, you could also say Я буду идти через лес.