What is the definition of Psi?

The twenty-third letter of Classical and Modern Greek and the twenty-fifth letter of Old and Ancient Greek.

Alright class, settle down now, let’s take a peek, At this little symbol – “psi” is what we seek! Now, the dictionary's right, it’s true you see, It comes from Greek, for you and me. Twenty-third in Classical style, And twenty-fifth in Ancient while! But let’s go a little deeper, don’t you think? “Psi” represents a sound, a special link! It's pronounced like "sigh," with a gentle plea, A breath of air, for all to see. Think of ancient scripts, and letters bold, "Psi" was a vital part, a story told. So remember this, my clever crew, “Psi” is Greek – it’s perfectly true! Do you have any questions about this letter's grace?

Psilorhynchus is a genus of fish in the family Psirrhacidae, which includes several species commonly known as pufferfishes or red polefin fish.

Psilorhynchus

Psittaci, a group of birds known for their distinctive call, are characterized by their long, pointed bills and their ability to fly high into the sky.

Psittaculidae

Psilosiphon is a type of fish that has a hard, spiky body with scales that help it swim and hide from predators. It's often found in freshwater environments like lakes or rivers where it can survive without water.

Psilosiphon

Psittacinepox is a disease caused by a virus that affects the respiratory system of birds, specifically psittacines (birds). It primarily affects the lungs and causes inflammation, leading to coughing, breathing difficulties, and sometimes death. This disease can be transmitted from one bird to another through droppings or contaminated food.

Psittacinepox

Psittacanthus is a type of insect known for its unique wingspan, which can reach up to 6 inches in length and include multiple sets of wings. These insects are often found in forests, gardens, or even on buildings due to their ability to climb high.

Psittacanthus

PsinSNPV is a type of protein in the human body, which plays a crucial role in metabolism and immune function. It consists of four amino acids (alanine, leucine, valine, and proline) and has a hydrophobic region at one end that binds to cholesterol molecules.

PsinSNPV

Psiloxyleae are a family of flowering plants in the family Apiaceae, known for their large leaves that have the ability to produce silage. These plants are native to North America and are used in agriculture for their high protein content and associated benefits like improved soil health and reduced reliance on chemical fertilizers.

Psiloxyleae

Psilosphaeria is a type of bacterium that can cause infections in various parts of the body, primarily affecting the respiratory system and skin. They are known for their ability to spread through contaminated water supplies or food, leading to severe illnesses such as pneumonia and meningitis.

Psilosphaeria

Psilocybin is a psychoactive substance found in mushrooms, primarily known for its hallucinogenic effects and psychedelic properties.

Psilonebria