Эта зима мягче, чем прошлая.

Because зима is a feminine noun.

In Russian, words like this must agree with the noun they describe:

• этот = masculine
• эта = feminine
• это = neuter
• эти = plural

Since зима is feminine, you say:

• эта зима

Both words are also in the nominative singular, because зима is the subject of the sentence.

Мягче is the comparative form of мягкий.

So:

• мягкий = soft / mild
• мягче = softer / milder

In this sentence, Russian uses the comparative form directly, just like English milder:

• Эта зима мягче = This winter is milder

By contrast, мягкая is just the regular feminine form of the adjective:

• мягкая зима = a mild winter

So мягкая describes the noun normally, while мягче compares it to something else.

It is formed as an irregular-looking comparative.

From мягкий, the comparative is:

• мягче

This involves a stem change:

• the final к changes to ч

This kind of change is common in some Russian comparatives.

A useful thing to remember: comparative forms like мягче do not change for gender, number, or case.

So you can say:

• зима мягче
• погода мягче
• дни мягче

The form мягче stays the same.

Yes, you could say:

• Эта зима более мягкая, чем прошлая.

This is grammatically correct and means the same thing.

Russian has two main ways to make comparatives:

1. Simple comparative
   
   • мягче
2. Analytical comparative
   
   • более мягкая

In many everyday sentences, the simple comparative (мягче) sounds more natural and compact.

So Эта зима мягче, чем прошлая is the most typical phrasing.

Чем is the word used for than in comparisons.

So:

• мягче, чем прошлая = milder than last one

A very common Russian comparison pattern is:

• X + comparative + чем + Y

For example:

• Он выше, чем я. = He is taller than I am / me.
• Сегодня теплее, чем вчера. = Today is warmer than yesterday.

So in your sentence, чем introduces the thing being compared to: прошлая (зима).

Because Russian often leaves out a noun when it is obvious from context.

Here, прошлая means:

• the last one
• literally: the previous [winter]

The noun зима is omitted because it would be repetitive:

• Эта зима мягче, чем прошлая зима. — possible, but less natural
• Эта зима мягче, чем прошлая. — more natural

English does the same thing sometimes:

• This winter is milder than last year’s
• This one is better than the previous one

So прошлая is functioning like the previous one, with зима understood.

Because it still agrees with the omitted noun зима.

Even though зима is not repeated after чем, it is still understood. Since зима is feminine singular, the adjective must also be feminine singular:

• прошлая = feminine singular
• understood noun: зима

So literally the structure is something like:

• This winter is milder than the previous [winter].

It is in the nominative singular feminine.

That may seem surprising, because English learners often expect a special case after than. But with чем, Russian usually keeps the compared word in the form it would have in the full comparison.

Here the full idea is something like:

• Эта зима мягче, чем прошлая зима (была).

Since прошлая зима would be nominative, the shortened прошлая also stays nominative.

Because Russian normally omits the present-tense form of to be.

In English, you say:

• This winter is milder than last one.

In Russian, the present-tense is is usually not said:

• Эта зима мягче, чем прошлая.

This is completely normal.

Compare:

• Он высокий. = He is tall.
• Она дома. = She is at home.
• Эта зима мягче. = This winter is milder.

Russian does use forms of to be in the past and future, but usually not in the present.

Here it means last or previous.

The adjective прошлый / прошлая / прошлое often means:

• previous
• last
• past

In this sentence, the most natural English idea is:

• last winter
• the previous winter

It does not mean final. For that idea, Russian would use a different word, such as последний, depending on context.

So here прошлая means the winter before this one.

No, Russian word order is fairly flexible, though some orders sound more natural than others.

The sentence:

• Эта зима мягче, чем прошлая.

is the neutral, natural order.

It starts with эта зима because that is the topic: this winter.

You may see other word orders in context for emphasis, but the standard version is the one given.

For learners, it is best to treat this pattern as the default:

• [subject] + [comparative] + чем + [comparison]

A helpful pronunciation guide is:

• Эта зима мягче, чем прошлая.
• EH-ta zee-MA MYAKH-che, chem PROSH-la-ya

A few notes:

• мягче is pronounced roughly MYAKH-che
• ч is like ch in chair
• чем sounds like chem
• the stress is:
  • зимá
  • мя́гче
  • прóшлая

You do not pronounce every letter exactly as in English spelling, so it is best to learn the word by ear as well.

Yes. This is a very common Russian pattern.

Structure:

• [This/that + noun] + comparative + чем + [other noun/adjective phrase]

Examples:

• Это лето жарче, чем прошлое.
  This summer is hotter than the last one.

• Этот дом выше, чем тот.
  This house is taller than that one.

• Сегодня холоднее, чем вчера.
  Today is colder than yesterday.

So your sentence is a very useful model for making comparisons in Russian.