Some nouns ending in 'y' after a consonant are made plural by changing the 'y' to 'i' and adding 'es', such as 'berry' to 'berries'. Some nouns are pluralized by internal vowel change, while some have the same singular and plural form without adding 's' or 'es', like 'sheep'. Additionally, some nouns only take 's' in their plural form and are not used in their singular form, including 'glasses' and 'thanks'.