אלמלא מדד האופטומטריסט את המרחק בין האישונים, העדשות לא היו מתאימות.

אלמלא means had it not been for... / if ... had not.... It introduces a counterfactual condition: something did happen, and the sentence says what the result would have been if it had not happened.

So:

אלמלא מדד האופטומטריסט...
= Had the optometrist not measured...

This is a fairly formal/literary word in modern Hebrew.

Because the sentence is talking about a completed action in the past: the optometrist measured the distance.

מדד = he measured

In Hebrew past tense, the verb agrees with the subject in gender and number:

• מדד = he measured
• מדדה = she measured
• מדדו = they measured

Since האופטומטריסט is treated as masculine singular, מדד is the correct form.

את marks a definite direct object.

Here, the direct object is המרחק = the distance, which is definite because of ה־.

So:

• מדד מרחק = measured a distance
• מדד את המרחק = measured the distance

Hebrew uses את only with definite direct objects, not with indefinite ones.

Because it means the optometrist, not an optometrist.

ה־ is the definite article, like the in English.

So:

• אופטומטריסט = an optometrist / optometrist
• האופטומטריסט = the optometrist

The sentence assumes a specific optometrist is being talked about.

It means between the pupils.

• בין = between
• אישונים = pupils (of the eyes)
• האישונים = the pupils

So המרחק בין האישונים is the distance between the pupils, which is exactly the measurement an optometrist needs when fitting lenses.

Because the sentence refers to a specific pair of pupils: the person's pupils whose distance is being measured.

So Hebrew says:

בין האישונים = between the pupils

This is natural because the phrase refers to a known, specific anatomical pair, not just any pupils in general.

Because the subject is העדשות = the lenses, which is feminine plural.

Hebrew words that describe the subject must agree with it in gender and number.

• עדשה = lens (feminine singular)
• עדשות = lenses (feminine plural)

So:

• מתאימה = suitable/fitting (feminine singular)
• מתאימות = suitable/fitting (feminine plural)

And היו is the past plural form of to be, so:

לא היו מתאימות = were not suitable / would not have fit

Here it functions like a predicate adjective or participle meaning suitable, matching, or fitting.

The root is related to התאמה / להתאים, meaning to fit, to suit, or to match.

So:

העדשות לא היו מתאימות
literally: the lenses were not suitable/fitting

In natural English, because of the counterfactual setup, we usually translate it as:

the lenses would not have been suitable
or
the lenses would not have fit

Hebrew often does not use a special word equivalent to English would have in this kind of counterfactual sentence.

Instead, the counterfactual meaning comes from:

1. אלמלא in the first clause
2. the past-tense structure in the second clause
3. the overall context

So although Hebrew says literally something like:

Had the optometrist not measured..., the lenses were not suitable

the meaning is understood as:

Had the optometrist not measured..., the lenses would not have been suitable

This is a very normal difference between Hebrew and English.

It is understood, but it sounds formal, bookish, or elevated.

In more everyday Hebrew, people might say something like:

אם האופטומטריסט לא היה מודד את המרחק בין האישונים, העדשות לא היו מתאימות.

That is more conversational.

So אלמלא is useful to know, but it belongs more to formal written Hebrew, careful speech, and literary style.

Yes. Hebrew word order is somewhat flexible.

This sentence begins with the condition:

אלמלא מדד האופטומטריסט את המרחק בין האישונים, העדשות לא היו מתאימות.

But Hebrew can sometimes rearrange parts for emphasis or style. Still, this order is very natural because it presents:

1. the condition first
2. the result second

That mirrors English structures like:

Had the optometrist not measured..., the lenses would not have fit.

It has two parts:

1. Condition
   אלמלא מדד האופטומטריסט את המרחק בין האישונים
   = Had the optometrist not measured the distance between the pupils

2. Result
   העדשות לא היו מתאימות
   = the lenses would not have been suitable / would not have fit

So the overall pattern is:

אלמלא + past verb, ... past/result clause

This is a standard way to express a past counterfactual in formal Hebrew.