Olá, collo o fío por aquí por iso de non chegar á 'profundidade máxima 
dos nosos lectores de correo'. 

Visto que non se chega a consenso, vou facer un repaso con máis profundidade 
do asunto replantexar a miña postura, que espero que poida ser de consenso.  

Hai propostas: 

1. Non hai diferenzas conceptuais entre os temos logo a tradución debe ser 
igual

2. Diferentes combinacións de 'complemento', 'extensión' e 'engadido' para 
'add-on', 'plug-in' e 'extension'. (creo recordar).

Persoalmente, creo que por motivos prácticos hai que definir termos separados 
pero tamén por motivos conceptuais, que son só matices. 

Primeiro, exactamente como se define cada termo: plug-in, add on & extension 
(Nota: procurei tanto 'add on' coma 'add-on' e 'plugin' e 'plug in', por se 
houber diferenzas)


Add-on

        Collins Cobuild English Dictionary

        add on

        If one thing is added on to another, it is attached to the other thing, 
or is 
        made a part of it.
        Holidaymakers can also add on a week in Majorca before or after the 
cruise...
        To the rear is a large dining room.added on early this century.
        PHRASAL VERB: usu passive, V P n, V-ed P
        If you add on an extra amount or item to a list or total, you include 
it.
        Many loan application forms automatically add on insurance.
        PHRASAL VERB: V P n (not pron), also V n P


        Collins Cobuild English Dictionary

        add-on

        An add-on is an extra piece of equipment, especially computer 
equipment, that 
        can be added to a larger one which you already own in order to improve 
its              
                performance or its usefulness.
        Speakers are sold as add-ons for personal stereos...
        N-COUNT: oft N n


        Oxford Advanced Learner's Dictionary

        add-on

        noun
        a thing that is added to sth else:
        The company offers scuba-diving as an add-on to the basic holiday 
price. *              
                add-on software (= added to a computer)

                
        WordNet

        add-on

        n 1: a component that is added to something to improve it; "the
        addition of a bathroom was a major improvement"; "the   
        addition of cinammon improved the flavor" [syn: {addition},
        {improver}]
        2: a supplementary component that improves capability [syn: {accessory},
        {appurtenance}, {supplement}]


Plugin

        Collins Cobuild English Dictionary

        plug in
        (plug in or plug into)

        If you plug a piece of electrical equipment into an electricity supply 
or if    
        you     plug it in, you push its plug into an electric socket so that 
it can            
                        work.

        PHRASAL VERB: V P n (not pron), V n P, V n P n
        If you plug one piece of electrical equipment into another or if you 
plug it    
        in, you make it work by connecting the two.
        
        PHRASAL VERB: V n P n, V P n (not pron)
        If one piece of electrical equipment plugs in or plugs into another 
piece of    
        electrical equipment, it works by being connected by an electrical cord 
or                      
        lead to an electricity supply or to the other piece of equipment.

        
        PHRASAL VERB: V P n, V P
        If you plug something into a hole, you push it into the hole.
        Her instructor plugged live bullets into the gun's chamber.
        PHRASAL VERB: V n P n


        Free On-Line Dictionary of Computing

        plugin
        plug-in

        A file containing data used to alter, enhance, or
        extend the operation of a parent {application program}. One
        of the first uses of this term was in {Silicon Beach}'s
        {SuperPaint} application (late 1980s?) for the {Macintosh}.
        It had a Plug-ins {folder} containing different tools and
        effects.
        The {Netscape Navigator} {World-Wide Web} {browser} supports
        plug-ins which display or interpret a particular file format
        or {protocol} such as {Shockwave}, {RealAudio}, {Adobe  
        Systems, Inc.} {PDF}, {Corel CMX} ({vector graphics}). The
        file to be displayed is included in a {web page} using an
        EMBED {HTML} {tag}.
        Plug-ins, both commercially and indepently authored, can        
        usually be downloaded for free and are stored locally.
        Plug-ins come in different versions specific to particular
        {operating systems} 


Extension

        Free On-Line Dictionary of Computing

Responderlle a