Many people have asked, "Elohim" אֱלֹהִים appears plural with the ending '-im'. Therefore, they believe this is an error. Or some use this to mock the Christian God saying it is God in the plural.
However, allow me to use my understanding of Hebrew to explain why Elohim when it is used for the God of Israel, it is always SINGULAR.
Like Greek, in Hebrew, the adjective must always agree with the noun. What this simply means is: when you use an adjective for a plural noun, the adjective must follow the grammatical number (either singular or plural) of the noun.
We have lost this in English, except for one or two examples, like you cannot say, "This are the men who came to school this morning." Automatically, you know something is not write and you have to swap the word 'This' with 'These'.
In Hebrew, if the noun is plural, the adjective also must appear in the plural form. Therefore, we have the example of:
נְעָרִים טוֹבִים
This means, "Good young men".
The adjective טוֹבִים (טוֹב means 'good') is in the plural; hence, the adjective in this case, 'agrees' with the plural noun 'young men'.
More examples here:
NOW, once you understand that the Hebrew noun and adjective must agree (plural noun/plural adjective and singular noun/singular adjective), we then see how the word גָּדוֹל which means 'great' does not appear as a plural adjective. This is because it could never be the case when Elohim when referring to the God of Israel is in the singular.