Learn Hardcore Russian: Вчерашний ужин был лёгким и вкусным.

In this sentence, лёгким and вкусным are predicate adjectives after the past-tense form of быть (был).
In Russian, predicate nouns and adjectives after быть can be either:

Nominative:
- Ужин был лёгкий и вкусный.
Instrumental:
- Ужин был лёгким и вкусным.

Both are grammatically correct here.

Very broadly:

Nominative often feels a bit more neutral or descriptive.
Instrumental often suggests a state or quality that something has (often understood as more situational or “as” something), and is extremely common in everyday speech.

In modern colloquial Russian, many speakers use both forms almost interchangeably in sentences like this, and the difference in nuance is small. So был лёгким и вкусным is a perfectly normal, natural way to say it.

So can I also say Вчерашний ужин был лёгкий и вкусный? Is there any difference in meaning?

Yes, you can say:

Вчерашний ужин был лёгкий и вкусный. (nominative)
Вчерашний ужин был лёгким и вкусным. (instrumental)

Both mean the same thing in everyday conversation.

Subtle nuance (which many native speakers do not consciously feel):

Nominative (лёгкий, вкусный) can sound like a simple, matter‑of‑fact description.
Instrumental (лёгким, вкусным) can sound a bit more like you are describing the quality or state the dinner had at that time.

For practical purposes as a learner, you can treat both as correct and natural in this sentence.

Why is ужин masculine, and how do I know that?

In Russian, ужин (dinner) is a masculine noun.

Clues:

It ends in a consonant in the nominative singular (ужин).
Most nouns ending in a hard consonant (like н) are masculine.
You can see masculine agreement:
- вчерашный ужин (masculine adjective ending -ый)
- ужин был (masculine past of быть: он был, ужин был)

General tip:

Masculine: usually ends in a consonant (стол, город, ужин).
Feminine: often ends in -а / -я (книга, неделя).
Neuter: often ends in -о / -е (окно, море).

There are exceptions, but this rule works for most nouns you meet at first.

What is the difference between вчерашний and вчера?

вчера is an adverb meaning yesterday (when something happened):
- Мы ужинали вчера. – We had dinner yesterday.
вчерашний is an adjective meaning yesterday’s / of yesterday:
- вчерашний ужин – yesterday’s dinner
- вчерашний фильм – the film from yesterday

So вчерашний ужин literally means the dinner of yesterday, i.e. yesterday’s dinner.

You would not normally say ужин вчера as a single noun phrase. You would say something like:

Наш ужин вчера был лёгким и вкусным. – Our dinner yesterday was light and tasty.

Could the word order be different, for example Ужин вчерашний был лёгким и вкусным or Вчерашний ужин лёгким и вкусным был?

Russian word order is more flexible than English, but not all orders sound equally natural.

Вчерашний ужин был лёгким и вкусным. – completely natural.
Ужин вчерашний был лёгким и вкусным. – possible in special contexts, with вчерашний emphasized (for example, contrasting with another dinner: not today’s, but yesterday’s dinner). It sounds somewhat marked.
Вчерашний ужин лёгким и вкусным был. – grammatically possible, but feels poetic or stylized. In normal conversation you generally would not say it this way.

As a learner, stick with Вчерашний ужин был лёгким и вкусным. It is the standard, most natural order.

Can I omit был, like in the present tense, and say Вчерашний ужин лёгким и вкусным?

No, in the past tense you normally must include был (or была, было, были).

Present tense:
- Ужин лёгкий и вкусный. – The dinner is light and tasty.
  (No есть; Russian usually drops the present‑tense быть.)
Past tense:
- Ужин был лёгким и вкусным. – The dinner was light and tasty.
  (You must use был.)

So Вчерашний ужин лёгким и вкусным without был is incorrect in standard Russian.

What is the difference between лёгкий as in this sentence and лёгкий meaning light in weight?

The adjective лёгкий has several related meanings. Two common ones:

Light in weight:
- лёгкий чемодан – a light suitcase (not heavy)
Light (not heavy/rich) food; easy to digest:
- лёгкий ужин – a light dinner (not heavy, not greasy, not large)

In Вчерашний ужин был лёгким, the context (dinner) tells us it is about the lightness of the meal (not heavy or rich), not the physical weight of an object.

Why does лёгким end with -им, while вкусным ends with -ым?

Both лёгким and вкусным are masculine singular instrumental adjective forms, but they belong to two slightly different patterns:

лёгкий → лёгким (soft‑stem / -ий pattern)
вкусный → вкусным (hard‑stem / -ый pattern)

Rough rule:

Adjectives ending in -ый usually take -ым in the masculine/neuter instrumental singular:
- новый → новым
- вкусный → вкусным
Adjectives ending in -ий usually take -им in the masculine/neuter instrumental singular:
- синий → синим
- лёгкий → лёгким

So the different endings just follow their respective declension patterns.

Why is вкусным also in the instrumental case?

Because лёгким and вкусным both describe the same noun (ужин) and are linked by и:

ужин был лёгким и вкусным

In Russian, coordinated adjectives that describe the same noun and have the same syntactic role should be in the same case, number, and gender:

Case: instrumental (predicate after был here)
Number: singular (one dinner)
Gender: masculine (ужин is masculine)

So you cannot mix cases like лёгким и вкусный; it must be лёгким и вкусным (or both in nominative: лёгкий и вкусный).

Why is лёгким written with ё, and do Russians always write it that way?

In standard spelling, the correct form is лёгкий, лёгким with ё.

However, in many printed texts, Russian often replaces ё with е, so you will see:

легкий, легким

Even when it is written е, it is pronounced as ё in this word.

So:

Spelling in learning materials and dictionaries: лёгкий, лёгким
Spelling you may often see in books/newspapers: легкий, легким
Pronunciation: [лёхкий], [лёхким] (approximately LYOG-kee, LYOG-keem)

As a learner, it is safer and clearer to always write ё when you know it should be pronounced that way.

How do you pronounce the whole sentence?

A simple approximate pronunciation (stressed syllables in capitals):

Вчерашний – vchye-RAHSH-nee
ужин – OO-zheen
был – byl (like English bill, but shorter and tenser)
лёгким – LYOG-keem (YO as in yoga)
и – ee
вкусным – FKOOS-nym (the в merges a bit with к; sounds like fkoos-nym)

All together:
vchye-RAHSH-nee OO-zheen byl LYOG-keem ee FKOOS-nym

Are there short forms of лёгкий and вкусный, like лёгок, вкусен, and can I use them here?

Yes, both adjectives have short forms:

лёгкий → лёгок (masc. short form)
вкусный → вкусен (masc. short form)

So you could say:

Вчерашний ужин был лёгок и вкусен.

This is grammatically correct but sounds more literary, bookish, or a bit old‑fashioned in everyday speech.

In normal modern conversation, Russians usually use the long forms:

Вчерашний ужин был лёгким и вкусным.
or … был лёгкий и вкусный.

As a learner, it is better to focus on the long forms first; short forms are less frequent and more stylistically marked.

What are the corresponding words for other meals, and would the grammar be the same?

Common meal nouns:

завтрак – breakfast (masculine)
обед – lunch / main midday meal (masculine)
ужин – dinner / evening meal (masculine)

The grammar would be the same:

Вчерашний завтрак был лёгким и вкусным. – Yesterday’s breakfast was light and tasty.
Вчерашний обед был лёгким и вкусным. – Yesterday’s lunch was light and tasty.
Вчерашний ужин был лёгким и вкусным. – Yesterday’s dinner was light and tasty.

In each case, вчерашний agrees in gender and case with the meal noun (all are masculine nominative here), and the predicate adjectives agree with that noun in gender, number, and case.