meso-, mes-, mesi-

(Greek: middle, intermediate; close to a center line; between)

1. A class of elementary particles whose masses are generally between those of the lepton class of lighter particles and those of the baryon class of heavier particles.
2. Any member of a family of subatomic particles composed of a quark and an antiquark.

A quark is a group of subatomic particles thought to be among the fundamental constituents of matter; more specifically, of protons and neutrons.

An antiquark is the antiparticle (atoms made up of antiprotons and antineutrons in a nucleus surrounded by positrons) of a quark. When a quark and an antiquark are brought together, mutual annihilation occurs.

Located in or referring to the middle of the nose.
A rare tumor of the female genital tract, most often the ovary.
mesonephros, mesonephra, mesonephroi
1. The second of the three excretory organs that develop in a vertebrate embryo, becoming the functioning kidney in fish and amphibians but replaced by the metanephros (embryonic organ of excretion in reptiles, birds, and mammals that develops into the kidney) in higher vertebrates.
2. The second type of excretory organ to develop in the vertebrate embryo.

It consists of a series of twisting tubules which arise from the mephrogenic cord caudal to the pronephros and that at one end from the glomerulus and at the other connect with the excretory mesonephric duct.

The organ is the permanent kidney in lower animals, but in human and various other mammals it is functional only during early embryonic development and is later replaced by the metanephros, although the duct system is retained and incorporated into the male reproductive system.

"Middle Claws", an extinct family of medium to large-sized omnivorous-carnivorous mammals closely related to artiodactyls (even-toed ungulates) which existed in North America and Eurasia over 33 million years ago.
1. The upper limit and the coldest portion of the mesosphere which is considered to be the transition zone between the mesosphere and the thermosphere.

The mesosphere is the region immediately above the stratosphere and just below the thermosphere.

2. A transition layer of the atmosphere (at an altitude of about 80 km) between the mesosphere, where the temperature decreases with altitude, and the thermosphere, where the temperature increases with altitude; so the mesopause is a level of minimum temperature.
mesopelagic (adjective) (not comparable)
Relating to the intermediate ocean depths between about 200 and 1,000 meters (656 and 3,280 feet): Mesopelagic organisms.exist in the sea between the photic epipelagic and the photic bathypelagic zones.
Fixation or attachment of a torn or incised (cut or broken) mesentery (membranes which connect the intestines and their appendages with the dorsal wall of the abdominal cavity).
1. An organism living in the moderate temperature range around that of warm-blooded animals, usually between 20-45 degrees Centigrade (77°F and 104°F).
2. A microorganism with an optimum growth temperature that is between 20°C and 45°C (77°F and 104°F).

The living areas of such organisms include soil, the human body, animals, etc.

The most desirable temperature of many pathogenic mesophiles is 37°C (98°F), the normal human body temperature.

mesophloem, mesophloeum
Middle, smooth, or green bark.
1. The photosynthetic tissue of a leaf, located between the upper and lower epidermis or the middle and photosynthetic tissue of a leaf.
2. The part of a leaf between the two thin surface layers, containing the cells responsible for photosynthesis.
1. Referring to the photosynthetic tissue of a leaf, located between the upper and lower epidermis.
2. Having leaves of moderate size, between microphyllous (very small) and macrophyllous (very large).
1. A plant which is adapted to grow under adequate conditions of water supply.

In drought, conditions wilting is soon apparent as the plants have no special mechanisms to conserve water.

Most angiosperms are mesophytes. Angiosperms include all agricultural crops (including the cereal grains and other grasses), all garden flowers and most horticultural plants, all the common broad-leaved shrubs and trees, and all the usual field, garden, and roadside weeds.

2. Terrestrial plants which are adapted to neither a particularly dry nor a particularly wet environment.

An example of a mesophytic habitat would be a rural temperate meadow.

Mesophytes generally require a more or less continuous water supply and they usually have larger, thinner leaves compared to xerophytes (dry plants), sometimes with a greater number of stomata on the undersides of the leaves.

Because of their lack of particular xeromorphic adaptations, when they are exposed to extreme conditions they quickly lose water, and don't survive in drought or very dry weather and they require very medium amounts of moisture.

A reference to the soft tissue (green parenchyma or the primary tissue) inside a leaf, between the lower outer leaf and the upper part of the leaf.

The soft tissue is involved with photosynthesis.

mesopia, mesopia vision
The ability to see in the "twilight range", between the photopic (eyes adapted to brighter light) and the scotopic vision (eyes adapted to low illumination or darkness).