helio-, heli-

(Greek: sun)

heliometry (s) (noun), heliometries (pl)
The use of a telescope with a movable split-lens objective, primarily to measure the angular distance between two stars; originally used to measure the diameter of the sun.
heliopathy (s) (noun), heliopathies (pl)
A physical injury from too much exposure to sunlight: Kitty stayed out too long in the sun while at the swimming pool and her skin suffered from heliopathy because it became very red and sore, and some of her skin even got blisters!
heliopause (s) (noun), heliopauses (pl)
1. The outer boundary of the sun where the solar or interplanetary magnetic environment gives way to the interstellar: In astronomy, the heliopause is the outside edge or boundary of the heliosphere, the part of our solar system that's influenced by the sun.

The orbits of all the major planets, including Earth's, lie well within the heliopause.

Astronomers have various theories about what happens beyond the heliopause, at such a far distance from the sun that solar wind doesn't affect anything.

Inside the heliopause is the heliosphere, and everything outside of the heliopause is considered interstellar space.

2. Etymology: The word heliopause is rooted in the Greek word for "sun," helios, and the Latin pausa, "a halt, a stop, or a cessation."
heliophil (s) (noun), heliophils (pl)
Any creature that lives or thrives in full sunlight.
heliophile (s) (noun), heliophiles (pl)
1. Any living creature or vegetation that is well-adapted to or thrives in full sunlight conditions: A heliophile can be an aquatic alga that is suited to reach maximum exposure to the light of the sun.
2. An individual who finds much pleasure in sunny weather: Toby's next-door neighbor was a heliophile who used every moment to be outside when the sun was out.
heliophilic (adjective), more heliophilic, most heliophilic
A reference to any organism or plant t is alive, well-adapted to, or thrives in full sunlight: Rosemary is a heliophilic plant that loves growing in the sun, along with purple coneflower and yarrow.
heliophilous (adjective), more heliophilous, most heliophilous
In biology, a reference to the existence of plants and animals in sunlight or under conditions of a high intensity of light: A heliophilous situation occurs in some desert organisms that have adapted to both strong sunlight and to drought.
heliophily (s) (noun), heliophilies (pl)
The existence of living plants and animals that are adapted to and thrive well in an environment of sunshine: When reading about heliophily, Judy found out that many very colourful flowers grow wonderfully in brilliant sunshine, like the hibiscus and the purple coneflower.
heliophobe (s) (noun), heliophobes (pl)
1. In biology, a plant that is intolerant of full sunlight and grows best in the shade.
2. In medicine, anyone who is abnormally sensitive to or has an exaggerated fear of the rays of the sun.
heliophobia (s) (noun), heliophobias (pl)
An irrational fear of sunlight or an abnormal sensitivity to the effects of sunlight resulting in a strong aversion to being exposed to the sun: In some cases, heliophobia may be influenced by the many warnings that people hear about skin cancer which can develop by being in the sun.
A strong aversion to sunlight.
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heliophobic (adjective), more heliophobic, most heliophobic
A reference to someone who has an exaggerated avoidance of the sun's rays: Linda, according to the doctor's explanation that she was heliophobic, definitely shunned the bright beams of light by wearing dark glasses or shades at all times and even stayed inside whenever the Sol was out.
An abnormal fear of the sun.
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heliophyll (s) (noun), heliophylls (pl)
The leaves of plants which require full sunlight in order to survive and to thrive.
A reference to plants that have leaves that can tolerate full sunlight.
A plant that flourishes under conditions of full sunlight.
A descriptive reference to a plant that flourishes under conditions of full sunlight.

Related "sun" word family: sol-.