[tag resources Tanvin-1-09a]Tanvin[/tag] is an adverbial ending, which may be compared with the English adverbial suffix –ly in such words as ‘seriously,’ ‘truly,’ ‘really,’ etc. Just like hamze, tanvin is also exclusive to the Arabic loanwords.

In Arabic, tanvin has two main functions: 1) Indefinite marker, as in [tag resources Tanvin-1-06a]کتابٌ[/tag] (nominative), [tag resources Tanvin-1-07a]کتابً[/tag] (accusative), [tag resources Tanvin-1-07b]کتابٍ[/tag] (genitive) ‘a book’; 2) adverbial ending, as in [tag resources Tanvin-1-07c]مثلاً[/tag] ‘for instance, for example.’ In all these cases the ending is pronounced –an, hence the word tanvin ‘n-ization’—i.e., making sound like an “n.” In Persian, the usage of the tanvin as the indefinite marker is not exercised; that is to say, in Persian tanvin is exclusively an adverbial ending.

In its original Arabic usage, tanvin has different forms, such as ـاً , ـا , as in [tag resources Tanvin-1-12b]غالباً[/tag], [tag resources Tanvin-1-12c]غالبا[/tag] γāliban ‘predominantly,’ and ـة , as in [tag resources Tanvin-1-13a]نسبةً[/tag] nisbatan ‘relatively’ (variably transcribed as نسبة), etc.

In Persian tanvin is orthographically normalized as ـاً ; although occasionally some members of the older generation of scholars transcribe the word نسبة in its original Arabic form, and not as the Persian form [tag resources Tanvin-1-16b]نسبتاً[/tag]. Writing [tag resources Tanvin-1-16c]غالباً[/tag] as [tag resources Tanvin-1-17a]غالبا[/tag] is also common among them—all forms are correct (although, because of the omition of the [ _ً ], sometimes tanvin is erroneously pronounced as a final [–ā] and not as [–an]; as in, [tag resources Tanvin-1-18b]ابداً[/tag] abadan ~ [tag resources Tanvin-1-18c]ابدا[/tag] abadā ‘not at all, under no circumstances,’ [tag resources Tanvin-1-19a]aslan[/tag] ~ [tag resources Tanvin-1-19b]aslā[/tag] ‘in principle, essentially,’ etc.

Words may have a combination of [tag resources ps Madd-1-18d]مدّ[/tag] ,[tag resources ps Madd-1-18c]تشدید[/tag] ,[tag resources ps Madd-1-18b]همزه[/tag] ,[tag resources ps Madd-1-18a]تنوین[/tag] ; as in: [tag resources Madd-1-18e]اوّلاً[/tag], in which the و is mošaddad (‘having tašdid’; i.e., ‘geminated’), and the terminal alef has tanvin; [tag resources Hamze-2-40a]تأثّر[/tag], in which there is a combination of hamze and tašdid, etc.

همزه and تنوین are exclusive to Arabic and they may not be used in words of Persian origin. Hence, the erroneous, rather illiterate and unsophisticated usage of such words as دوماً ‘secondly,’ with the Persian number دو, is merely based on analogy with اوّلاً—a word of Arabic origin. In this case, either the Arabic adverbs [tag resources Hamze-2-45c]رابعاً[/tag] ,[tag resources Hamze-2-45b]ثالثاً[/tag] ,[tag resources Hamze-2-45a]ثانیاً[/tag], must be used or, otherwise, the Persian numbers must be used as follows: [tag resources Hamze-2-46a]نخست[/tag] naxost, noxost ‘first, firstly’, [tag resources Hamze-3-01a]دوم[/tag] dovom ‘second, secondly’, [tag resources Hamze-3-01b]سوم[/tag] sevom ‘third, thirdly,’ [tag resources Hamze-3-01c]چهارم[/tag] cahārom ‘fourth, fourthly,’ etc.

Also, bear in mind that the و in Persian numbers دوم dovom and سوم sevom must not be geminated. Therefore, the common pronunciation of these words as [tag resources Hamze-3-04a]دوّم[/tag] dovvom and [tag resources Hamze-3-04b]سوّم[/tag] sevvom is only on analogy with the geminated و in the Arabic اوّل awwal ‘first’ and اوّلاً awwalan ‘firstly’ (Persian avval, avvalan) (that is to say, dovom and sevom, without a geminated [v] are the correct pronunciations).