An auxiliary verb is a helping verb used to express tense, mood, or voice. The auxiliaries include have (has,had), be (am, is, are, was, were), do (does/did), and the modal auxiliaries (such as must, can, will, and should).
Some researchers assert that clockless processors will
soon become cheaper, more reliable, more energy efficient, and easier to design
than chips based on today's prevailing technology.
--W. Wayt, "Turning Back the Clock," Scientific American (modified)
Auxiliary verbs differ from other verbs in the way they are negated and in the positions they may occupy in the sentence.
You can negate a sentence or clause by placing the first auxiliary verb before the negative word not.
Virtually every developing country can point to examples of dilapidated
wind pumps or photovoltaic power systems that either did not work or
could not be repaired with local materials.
--Daniel Kammen, "Cookstoves for the Developing World," Scientific American
If you use more than one auxiliary verb in a verb phrase, place only the first auxiliary verb before not; place the rest after not.
If transistors had been not developed during the first
half of this century, the world in which we live would be drastically different
today.
If transistors had not been developed during the first
half of this century, the world in which we live would be drastically different
today.
You can negate a sentence or clause that does not contain an auxiliary verb by introducing the auxiliary do before not.
The planet Mercury tilts not, so it does not have
seasons.
The planet Mercury does not tilt, so it does not have
seasons.
--"Take It or Leave It," Valley Comic News (modified)
Remember that there are two have verbs, one an auxiliary and one a main verb. The auxiliary have is associated with perfect tense. The main verb have refers to possession, obligation, or causation. You can place only the auxiliary have before not; the main verb have must be negated with do.
The planet Mercury does not tilt, so it has not
seasons.
The planet Mercury does not tilt, so it does not have
seasons.
--"Take It or Leave It," Valley Comic News (modified)
How can physicists seek the massive particles that give
logic and symmetry to theories of the fundamental elements of matter?
--David B. Kline, "Low Energy Ways to Observe High-Energy Phenomena," Scientific American
