O connects transitive verbs to direct or indirect objects:

                  +----O----+
                  |         |
        The dog chased the cat

Words carrying O- include nouns, pronouns, and many other
kinds of words that can act as noun-phrases or heads of
noun-phrases. See "S". (In ths case of pronouns, only
accusative pronouns carry O-: "her", not "she".) O- on nouns
is directly disjoined with S+, since a noun cannot be both a
subject and an object.

Transitive verbs carry "O+". This is conjoined with other
left-pointing connectors which link to the subject (directly
or indirectly), such as S-, PP-, I-, Pg-. Some verbs have
optional O+ connectors; they may or may not be transitive ("We
moved"; "We moved it"). Some verbs can take an object followed
by some other complement; such verbs have other connectors
like Pa+, TOo+, I+, Pg+, or TH+ optionally conjoined with O+:

             +---?---+
             +-O-+   |
             |   |   |
        We made him do it   (I)
        We saw  him running   (Pg)
        We find him stupid   (Pa)
        We told him to leave   (TOo)
        We told him that he was in trouble   (TH)

Other verbs have two O+ connectors, one or both of which may
be optional ("I gave him five dollars", "I gave five
dollars"). In this case, the first object may either be a
pronoun or a noun; however, if it is a noun, the second may
not be a pronoun: "I gave him the money", "I gave Jane the
money", "*I gave Jane it", "*I gave him it". This is parallel
to the case of particles; in transitive verbs which take
particles like "up" or "out", the particle may not precede a
pronoun ("*We sorted out them").  The O*n+/Ox- subscripts,
developed for that purpose, are used here as well. The second
O+ connector on two-object verbs has O*n+; pronouns have Ox-;
"Oxn" is prohibited in post-processing. (See "K".)

The Os- and Op- connectors mark nouns as being singular or
plural. The main reason for this is to enforce the correct use
of "there is"/ "there are". The "O#t" subscript is related to
this as well. See "SF: 'There' as a subject".

The Ot- connector is used to constrain certain verbs to only
accept time expressions as an object:

         +----Ot-----+
         |      +-ND-+
         |      |    |
    it lasted five years

Osi and Opi are used in the construction:

              +------Bs----+
              +----R---+   |
           +SF+-Osi+   +-RS+
           |  |    |   |   |
        1.It  is Jane who wants to do it

Forms of "be" are thus able to take a noun (proper or common)
plus a relative clause. For the relative clause, we use the
same link-types (B, R, and RS) used in ordinary relative
clauses. Forms of "be" thus carry

is: Ss- & (Pg+ or Pv+ or O*t+ ... or (Osi+ & R+ & Bs+) or
        (Opi+ & R+ & Bp+))

Note that the O+ connectors used in this expression are
different from the ordinary O+ connector used in "It is a
dog".  Note also that there must be number agreement between
the noun and the verb of the relative: "*It is my father who
want to do it", "*It was my parents who wants to do it". This
is enforced by the linkage expressions above. There are other
constraints on this construction as well:

        2.*The man was John who did it
        3.*I saw John who did it
        4.*It wanted to be John who did it

In this construction, the subject must be "it" (see ex.2); the
main verb must be "be" (ex.3); and there are constraints on the
other verbs that may be used in the expression (ex.4). These
are the same constraints that are already in place for the use
of "filler-it". Thus we must simply add "Osi" and "Opi" to the
list of link-types that require "filler-it" as subject, and
everything else follows automatically. (See "SF: Filler-it".)

Regarding Om and O#c, see "MV: Comparatives", sections II
(Om) and III (O#c).