Difference between Stiffen and Constrain

STIFFEN vs CONSTRAIN: VERB

To inhibit or restrain; hold back.
To keep within certain limits; confine or limit.
To compel by physical, moral, or circumstantial force; oblige.
To produce in a forced or inhibited manner.
To secure by bonds; to chain; to bond or confine; to hold tightly; to constringe.
To bring into a narrow compass; to compress.
To hold back by force; to restrain; to repress.
To compel; to force; to necessitate; to oblige.
To violate; to ravish.
To produce in such a manner as to give an unnatural effect.

To make stubborn or obstinate.
To make more thick or viscous; inspissate: as, to stiffen paste.
To make rigid, constrained, formal, or habitual.
To make stiff.
To become higher in price; become firmer or more unyielding: as, the market stiffens.
To become unyielding; grow rigid, obstinate, or formal.
To become steady and strong: as. a stiffening breeze.
To become less soft or fluid; grow thicker or harder; become inspissated: as, jellies stiffen as they cool.
To become stiff.
Severely restrict in scope or extent
(transitive; intransitive verb) To make or become stiff or stiffer.

In general, to exert force, physical or moral, upon, either in urging to action or in restraining from it; press; urge; drive; restrain.
Hence To urge with irresistible power, or with a force sufficient to produce the effect; compel; necessitate; oblige.
To confine or hold by force; restrain from escape or action; repress or compress; bind.
To check; repress; hinder; deter.
To force.
In mech.: To prevent the occurrence of (motion), except in a particular direction: as, the relative motions of the parts of any machine are always constrained.
To prevent the operation of the motion of (a material point or body), except in a particular and definite manner: as, to constrain a part of a mechanism.
Compel to behave in a certain way
To close within bounds, or otherwise limit or deprive of free movement
Severely restrict in scope or extent

Lengthen, Slacken, Thicken, Weaken, Constrict, Soften, Harden, Loosen, Reinforce, Sharpen, Strengthen, Toughen, Tighten up, Constrain, Tighten

Constrict, Hinder, Circumscribe, Inhibit, Hamper, Undermine, Impede, Restrict, Curtail, Tighten up, Cumber, Stiffen, Tighten, Encumber, Restrain

Clench, Lengthen, Slacken, Thicken, Weaken, Constrict, Soften, Harden, Loosen, Reinforce, Sharpen, Strengthen, Tighten up, Constrain, Tighten

Impair, Constrict, Hinder, Circumscribe, Inhibit, Hamper, Undermine, Impede, Restrict, Curtail, Tighten up, Stiffen, Tighten, Encumber, Restrain

How do international capital markets constrain policy space?
UNIQUE constrain, because NULL is not a value.
Increased frequency of security patches can constrain operations.
Are historical records sufficient to constrain ENSO simulations?
United States to constrain China in the region.
The PCD TF does not further constrain thifield.
Did being a poet help or constrain you?
It may be a constrain in improving something that may be a constrain.
You can constrain the part instance to be fixed in space, or you can constrain it to follow selected nodes.
To constrain or not to constrain, and other stories of intensive upper extremity training for children with unilateral cerebral palsy.