Insidious means deceitful and cunning. You could use it in a sentence such as "His insidious plan to take over the world might actually work".
The insidious disease spread quickly throughout the village, causing panic and devastation among the residents.
The insidious spread of misinformation on social media has led to confusion and division among the population.
The insidious nature of the virus allowed it to spread undetected throughout the community.
You divide it like this: in-si-di-ous.
The insidiously flattering messages were designed to manipulate her emotions.
I can use the word "for" in a sentence to indicate a purpose or reason, such as "I am studying for my exam."
Morrie's disease "ALS" is insidious .
the investigators uncovered an insidious scheme to rob people of their money
Facetious or insidious
Plagiarism is an insidious habit.
The insidious spread of misinformation on social media has led to confusion and division among the population.
The insidious nature of the virus allowed it to spread undetected throughout the community.
Another word for "insidious" is the word "treacherous"[or "sly",or "crafty"].
The kindness of a con man is an insidious ploy to gain the trust of his victims.
You divide it like this: in-si-di-ous.
The insidious wickedness of the witch was ably portrayed.
Insidious
The insidiously flattering messages were designed to manipulate her emotions.