To be proper camel case a word with no digits allowed, a word:

• MUST start with a lower case alphabet (a through z)
• MUST have no digits (0 - 9)
• MUST have no spaces, punctuation or special characters
• CAN have at most 1 uppercase alphabet in a row
• MAY end in an uppercase alphabet

Notable examples

• a is valid lower camel case
• aG is valid lower camel case
• camelCase is valid lower camel case
• camelCasE is valid lower camel case
• aGa is valid lower camel case
• alphabet is valid lower camel case