>> >In our English book we have an example for gerund as follows:
>> > After leaving India he studied at London university.
>> >In my opinion >>leaving<< is not a gerund, any advice ?

>> I disagree with the other two replies I have seen.  The book is right;
>> "leaving" is clearly a gerund in this sentence.  It functions as a
>> noun, being the object of the preposition "after".

The distinction between the two terms "participle" and "gerund"
isn't really applicable to Modern English.  It's a traditional one
based on Latin morphology and syntax.

From: David Crystal's Glossary of linguistic terms (appendix to Oxford
University Press's International Encyclopedia of Linguistics, 1992 4Vol)

 Gerund: see Participle (V.4 p.302)

 Participle: In traditional grammar, a word derived from a verb and used
   as an adjective (e.g, 'a smiling face'); contrasts with the Gerund or
   verbal noun (e.g, 'Swearing is not allowed).

   In linguistics, the term is generally restricted to non-finite forms
   of a verb other than the infinitive; in English, often classified
   into Present and Past forms, or (where the temporal implication is
   inappropriate) into "-ing" and "-ed" forms (e.g, 'I'm running', 'I've
   walked').  (V.4 p.322)

The distinction between "Participle" and "Gerund" lies in their *use*,
not their form.  The Present Active Participle (the "-ing") form is the
only completely regularly inflected verb form in English. Every English
verb, even the canonically irregular 'be', has such a form, produced
simply by adding the -ing suffix to the infinitive root; there are no
exceptions (except modal auxiliaries, which are defective in English).

This verb form is used in a number of English constructions:
 1) as the next verb form after the "be" of the progressive aspect -

     I am walking    I have been walking    He is being photographed
       ^^     ^^^           ^^       ^^^       ^^   ^^^
       be Vb -ing           be   Vb -ing       be V-ing

    Unlike the other uses, this use is possible only with semantically
    Active predicates, e.g:

     I am renting a house (NB: does not distinguish lessor from lessee)
    *I am owning a house  ('own' is stative, while 'rent' is active)
 2) in adjectival clauses (typically reduced relative clauses) modifying
    noun phrases -

     Everyone owning a house was present.
     Everyone having a banana in their ear should report it.
     ^^^^^^^^    ^^^
     NounPhrs Vb-ing

    Note that this is equivalent to a relative clause constructions

      Everyone who owns a house was present.
      Everyone who has a banana in their ear should report it.

    but not to the ungrammatical

     *Everyone who was owning a house was present.
     *Everyone who is having a banana in their ear should report it.
 3) as the main verb in a "POSS -ing" or "Gerund" complement (i.e, a
    subordinate noun clause functioning as subject or direct object of a
    higher clause

      (His) Owning a red Corvette is significant.   (Subject complement)
      My accountant discourages (my) betting on the ponies. (Object ")

    This is one of the three forms of English complements.
    The other two are the "for-to" or "Infinitive" complement -

      (For me) To own a red Corvette would be something special. (Subj)
      My accountant says (for me) not to bet on the ponies.      (Obj)

    and the "that+S", or "Finite" complement -

      That I own a red Corvette is true, but irrelevant.         (Subj)
      My accountant thinks (that) I bet on the ponies.           (Obj)
    Note, in passing, that the gerund complementizer is distinctly
    "verby" -- i.e, the gerund form is a real (though non-finite) verb,
    which can take a subject (in the possessive case) and an object (in
    the objective), can be modified by adverbs, etc.  The complement
    clause is a noun phrase, but the gerund itself heads a verb phrase.
 4) as the head of an adverbial clause, often introduced by a subordinating
    conjunction, and usually without a subject. These, like complements, can
    take "have" to indicate they happened in the past:

      After looking into it, he decided there was no merit to it.
      (After) having looked into it, he decided there was no merit to it.
      Having captured the town, Caesar wrote a report.
      After having written the report, he took a nap.
      The malefactor, upon observing him, fled.
      Looking into it like this, you see a lot of strange things.

    This is the source of the famous "dangling participle", which refers to
    a participial phrase without a subject at the beginning of a sentence,
    whose subject is not the immediately next noun phrase, but something
    later in the sentence.  This produces effects like the classical:

      Sitting on the fence, my mother saw three cats howling.
 5) as a true noun, derived from a verb, i.e, a "verbal noun". This is
    usually called the "-ing" nominalizer, and it can't take an object:

     *The singing the National Anthem took place at 8 sharp.
      The singing of the National Anthem took place at 8 sharp.
    The NP that functions as direct object of the actual verb must
    show up in a prepositional phrase with a true nominalization;
    in addition, a true noun can take a definite article, whereas
    a verb can't.

The upshot of all this is that, while Latin has a Gerund, a Gerundive,
a Present Active Participle, a Perfect Passive Participle, and a Future
Active Participle, English just has two forms of the verb -- one with
-ing (and no irregularity), and one with -ed/-en (and considerable
irregularity) -- and they are each used in a number of constructions.

The -ing *form* is often called "gerund" (so that the -ed form can be
called just plain "participle"), but its various syntactic uses are
carefully distinguished and named in English.

No one, of course, is obliged to use any grammatical term (or for that
matter any other kind of term) the same way as anyone else.  However, if
one insists that a term must mean exactly what they expect it to mean,
they may often be disappointed in others' practice.

-John Lawler   http://www.umich.edu/~jlawler/aue    Michigan Linguistics
  "Latin. Man's natural language. Spoils your style. Useful for reading
   the inscriptions on public fountains.  Beware of quotations in Latin:
   they always conceal something improper."   -- Gustave Flaubert