Abbreviated groups are stored in a TAB-delimited text file called default.abbrevgroup. The basic format is:

    Ac	CC=O	2
    AcAc	CC(=O)CC(=O)	5
    Acet	CC=O	2
    Ade	NC1=C2N=CNC2=NC=N1	6	1
    J	C*.CCC[C@H](N)C=O |r,m:1:3.4|	7	8

In these lines the very first word is the abbreviation, the second is the CXSMILES string representing the molecule fragment depicted by the abbreviation. These are followed by the attachment atom numbers (in the CXSMILES string). In the first line using the Ac abbreviation the second carbon is the attachment atom so if we have a connection to an other molecule part then this atom will make the connection. If there is no number following the the CXSMILES string the abbreviated group can not be connected to other atoms. (However their number is not limited too since Marvin 6.0.)

Usually the bond points towards the middle of the abbreviation but when the string contains atom symbols, probably we want to make it point to the symbol of the bonding atom. Furthermore it is desirable to flip the abbreviation when the group is in the opposite side:

To achieve the flipping effect one have to provide the alternative name of the abbreviated group that will be printed on the left side of the molecule:

	CN	C#N	1	leftName=NC
	CO2Et	CCOC=O	4	leftName=EtO2C
	CO2H	OC=O	2	leftName=HO2C
	COOH	OC=O	2	leftName=HOOC
	COOiAm	CC(C)CCOC=O	7	leftName=iAmOOC

If the abbreviation contains numbers, those will be treated as subscripts:

	C10H21	CCCCCCCCCC	1	leftName=H21C10
	CBr3	BrC(Br)Br	2	leftName=Br3C

Additionally there can be groups where it is good to have flipping abbreviations but the string represents the form that is used on the left side. For these groups (for example AcO, MeO) the rightName specifier can be used:

	BnNH	NCC1=CC=CC=C1	1	rightName=HNBn
	BnO	OCC1=CC=CC=C1	1	rightName=OBn
	BnO2C	O=COCC1=CC=CC=C1	2	rightName=CO2Bn
        BnOOC	O=COCC1=CC=CC=C1	2	rightName=COOBn

If you do not want to flip an abbreviation but want to be sure that the bond points to an atom symbol and not to the middle of the string, you still can define the center specifier:

	c-C10H19	C1CCCCCCCCC1	1	center=AUTO
	c-C11H21	C1CCCCCCCCCC1	1	center=AUTO
	c-C12H23	C1CCCCCCCCCCC1	1	center=AUTO  

This option allows to point to the very first character in the abbreviated group string that is the same as the atom symbol of the binding atom. This option makes it possible to fine-tune the position of the bond to point to any of the characters.

Atom properties of the atoms inside the are stored int the CxSmiles description part of the molecule. But properties of the abbreviation atom can not be stored there: they are stored in a separate field with the same syntax as in the CxSmiles format. In the example below the abbreviation atom of Alanine contains two properties with keys 'property 1' and 'property 2' and values 'value 1' and 'value 2' correspondingly. Properties are separated by the character ':'. Characters '.' and ':' in property keys and values are escaped.

        Ala    C[C@H](N)C=O |r|    3    4    abbrevAtomProperties=property 1 .value 1:property 2.value 2