Learn Russian: Левое окно большое.

In Russian, the present tense forms of the verb 'to be' (like 'is', 'am', or 'are') are skipped. You just place the subject and its description next to each other. Literally, this sentence translates to 'Left window big.'

Why do the words левое and большое both end in -ое?

In Russian, adjectives must match the gender of the noun they describe. The dictionary forms for these words are левый (left) and большой (big). Because they are describing окно (window), which is a neuter noun, they must change to their neuter forms, ending in -ое.

How can I tell that окно is a neuter noun?

You can almost always tell a Russian noun's gender by looking at its last letter. Nouns ending in a consonant are usually masculine, those ending in -а or -я are feminine, and those ending in -о or -е are neuter. Since окно ends in -о, it is a neuter noun.

What happens if I change the word order to Большое окно левое?

It is grammatically correct, but it completely changes the meaning! Because Russian doesn't use words like 'the' or 'is', the word order tells us what the core subject is. Левое окно большое means 'The left window is big.' If you say Большое окно левое, it means 'The big window is the left one.'