Key difference: Mermaid and Siren are two mythical female creature known for their beauty and luring appearance. A "Mermaid" is a half-woman half-fish creature that lives in seas, while a Siren is a half-woman half-bird creature. Both have been a fascination in popular fiction literature for their beauty and alluring appearances. 

Mermaid and Siren stories have been heard and told through the 16th century and onwards. The beauty of these mythical creatures made them an indispensable part of popular folklore and fiction that still has influences on audiences today. Their habitat has often been shown as oceans and islands with their mysterious appearances as awfulized characters. Fairy tales and folk tales have always had these creatures interacting with other characters with the fascination that is dear to children as well as adults. The uniquely odd features of these creatures make them always "wanted to hear about" in popular stories and after the arrival of cinema, they were explored beautifully on motion picture screens. (See the difference between fairy tales and folk tales). Children are often seen asking elders - "are mermaids real" and "are sirens real?" Often, a mermaid and siren are considered to be the same and hence people remain confused between due to their similarities because they have influenced us in the same way fairy tales and folk tales did. This article might give a clear difference between their existence and features.

A 'mermaid' was a half human and half fish type of creature. Mermaids stories appeared in the folklore of many cultures worldwide, including the Near East, Europe, Africa, and Asia. Mermaids had a torso of a fish and the upper body of a human being. They were very beautiful, and had extreme attractive looks and facial features, as opposed to one’s normal presumption that their scales would make them look repulsive. They used to attract, hypnotize and seduce the sea sailors or navigators with their shrill and fascinating voices. These were humble and kind in nature, hence mermaids were always helpful towards humankind. Many mermaid videos are often faked on the internet as real videos which we often see going viral. 

A 'siren' was a half woman and half bird type of creature, which belonged to Greek mythology (See the difference between myth and mythology). They were nymphs who lived on islands surrounded by cliffs. Sirens were believed to combine women and birds in various ways. Like Mermaids, even sirens used to attract and seduce the sailors with their shrill voices by enchanting and singing different tunes. But, Sirens had wicked and evil intentions behind their motives, They used to drown the sailors into the sea. This proves that they were harmful and dangerous in nature.

Both these creatures had their mythical stories, mermaid and siren both were known for their beauties and different behavioral features. Note that they were not holy ghosts or holy spirits though they may be depicted that way (See the difference between a holy ghost and the holy spirit). They were the most attractive and seducing woman, hence men’s often used to get attracted towards them. These had their typical behaviors, like mermaids had golden long hairs, and often used to see themselves in mirrors or see reflections; they always used to play with their hairs. On the other hand, sirens were known for singing and seducing abilities, which attracted the males. Hence, sirens were considered to be more dangerous with evil wicked intentions than mermaids, who were gentle and kind towards humankind. Now that the world has advanced with the culture of increased scientific questioning people clearly distinguish between reality and myths & folk tales (See the difference between myths and folk tales), though both of them are narrated and heard with interest and entertainment. 

Comparison between Mermaid and Siren:

Also see: The difference between soul and spirit

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