1. Pears are in season.

2. Pears are out of season.
3. Persimmons are in fashion.
4. Persimmons are out of fashion.

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Are the expressions all grammatical? Can we use 'fashion' instead of 'seaon'?

Fashion and season have differing connotations. Season implies something nature produced, fashion implies something humans produced.

Her coat is out of fashion, considering the style and decorations.
Her coat is out of season, considering the lack of cold the past two months.

Season has other meanings: It means to make fit, as in ...Season her by giving more responsiblity.

Fashion implies something time and culture changes, miniskirts are an example of my generation....Her skirts are fashionably below the knee. His buttoned down cuffs are the fashion. In due course, as they aged, they no longer held hands on walks, as it was out of fashion.

I would not use fashion in the above, unless you mean the persimmions are out of favor with human usage. That is possible: Kiwi fruit is currently in fashion with the wine and dine set, but out of season here in Texas.

Bob Pursley is right.

You'd use "in season" with food, as you've done in sentences one and two.

The only reason you'd use "in fashion" in sentences three and four would be if you are using persimmons to decorate with -- perhaps in a table centerpiece.

=)

1. Pears are in season. - This sentence is grammatical and it means that pears are currently being harvested and are readily available.

2. Pears are out of season. - This sentence is grammatical and it means that pears are not being harvested currently and are not easily available.

3. Persimmons are in fashion. - This sentence is grammatical and it means that persimmons are currently trendy or popular.

4. Persimmons are out of fashion. - This sentence is grammatical and it means that persimmons are not currently trendy or popular.

Now, regarding your question about using "fashion" instead of "season," the answer is yes and no. While "fashion" and "season" can both be used to describe the availability or popularity of certain fruits, they convey slightly different meanings.

"Season" refers to the time of the year when a particular fruit is at its peak in terms of growth and availability. It typically relates to factors such as climate and agricultural cycles.

On the other hand, "fashion" refers to something being currently in vogue or trendy. It often relates to societal preferences and consumer demand.

So, when talking about fruits, "season" is more commonly used to describe the time when they are naturally available, while "fashion" is used to describe whether they are currently popular or trendy.

In summary, while you could use "fashion" in place of "season" to describe the popularity of certain fruits like persimmons, it would not accurately convey the same meaning as "season."